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Volume 76, 1946-47
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Ascidians in the Vicinity of the Portobello Marine Biological Station, Otago Harbour.

[Read before Otago Branch, April 9, 1945; received by Editor, March 13, 1946; issued separately, September, 1946.]

The coastal rocks at the point of the Portobello Peninsula, on which the Marine Biological Station is situated, support a particularly rich ascidian fauna. It would seem that the swift-flowing current which sweeps around this point provides the large volume of clean foodbearing water necessary to support such a wealth of filter-feeders, for, whilst a similar fauna occurs on the rocks at the side of the main harbour channel where it passes through the narrow gap between Goat and Quarantine Islands, elsewhere on the Peninsula and on the two islands ascidians are not only less numerous but also represented by fewer species. The present account is based on the study of the ascidians from the coastal rocks of all three localities mentioned: the Portobello Peninsula Point, Goat Island, and Quarantine Island.

Review of Literature.

Quoy and Gaimard, 1834 (Voy. de l'Astrolabe), described very briefly four species of ascidians, three simple and one compound.

Heller, 1878 (Sitz. Akad. Wien, lxxvii), gave an account of two additional species of simple ascidians.

Herdman, 1882 (Report of H.M.S. Challenger), added yet another two simple forms to the list.

Nott, 1892 (Trans. N.Z. Inst.), the first New Zealander to publish a paper on the group, described eight compound species from the Auckland Harbour.

Watt, in the same year and in the same journal, gave a detailed description of Pyura pachydermatina (Herdman).

Sluiter, 1900 (Report of Prof. Schauinsland's Pacific Expedition), described fourteen species from New Zealand and a further fourteen found in the Chatham Islands but not in New Zealand. Unfortunately, his accounts and illustrations are in some cases incomplete.

Cottrell, 1912 (Trans. N.Z. Inst.), published a detailed description of Cnemidocarpa coerulea (Quoy and Gaimard).

Michaelsen, 1922, 1924 (Report of Dr. Th. Mortensen's Pacific Expedition), not only described the ascidians collected by the expedition, but also, after examining type specimens, published further-details of many of the species previously recorded from New Zealand, the Chatham, and the Auckland Islands. These two volumes take the form of a monograph covering fifty-eight New Zealand species and an additional eight found on the Auckland or Chatham Islands. All specific descriptions are given with great care to detail, and it is unfortunate that, like his predecessor Sluiter, he was obliged to base his accounts on the study of preserved material; in some cases, only a

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few specimens being available, he was unable to give the range of variability of the species. However, in other cases where a large amount of material was to hand, he has shown that factors previously used for differentiation between species are subject to variation within the one species.

None of the marine biological expeditions mentioned above visited the coast between Christchurch and Stewart Island, and to date the only ascidian recorded from the Otago Harbour is Pyura pachydermatina. From a general survey of ascidians from Stewart Island, Lyttelton, and Auckland, and from a particular survey of those from the Otago Harbour, it is apparent that different ranges of variability occur in different localities, and that the systematics of the New Zealand ascidian fauna cannot be placed on a firm basis until a wider knowledge of the variability of the individual species is available. Hence it has been decided to limit the descriptions that follow to specimens from the district under survey alone. (An exception is made in the case of Pyura cancellata, where few specimens were found in the district and Auckland specimens were included to give sufficient data upon which to base the erection of a new species. In this case local differences are noted.)

Classification.

No general classification of the group has been published since 1911 (Hartmeyer and Seeliger in Bronn's Klassenu-Ordnungen des Thier-Reichs), and the classification in this article is based on this and on the more recent works of Hartmeyer, Arnbäck-Christie-Linde, Huntsman, Michaelsen, and Van Name.

Material and Methods.

During 1944 and the early part of 1945 many visits were paid to the Marine Biological Station for the purpose of making field notes and collecting material. Fortnightly dissections were made of all the common species in order to note presence or absence of tadpoles and to estimate the state of ripeness of the gonads, and all ascidian tadpoles found in the plankton samples taken over the same period were preserved for comparison with those found in the mantle cavities and common cloacal cavities of the adults. As, with the exceptions of Pyura cancellata and Pyura pulla, a large amount of material was available, in order to give an idea of the local range of variability, descriptions of the simple species are based on the study of at least twenty-five specimens. Small specimens unsuitable for dissection were avoided, and therefore members of the various species will be found with smaller dimensions than those given below. In describing simple forms, length is taken as a line parallel to that joining the apertures, breadth as the distance between right and left sides, and depth as the dorso-ventral measurement; the number of longitudinal vessels is given for the middle region of the pharynx; and the pharyngeal folds are numbered according to Michaelsen's plan, that next the endostyle being Number 1. In the compound forms measurements and proportions given are of expanded zooids, and the number of stigmata per row applies to one side of the pharynx only.

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Three per cent. formalin was the fixative most generally used. To preserve specimens in an expanded state, the following methods were used: For simple forms—either narcotisation with cocaine hydrochloride or rapid fixation with hot corrosive sublimate; for compound forms— rapid fixation in glacial acetic acid for three to five minutes. In compound forms individual zooids reacted in different ways to the fixative, but it was always possible to dissect out a few fully expanded ones. Quick determinations of the structure of the zooids of the soft compound forms were made by squeezing them directly from the living colony on to a slide covered by glycerine, and after ten minutes covering, examining them under the microscope with a certain amount of pressure on the cover glass. This method was found to be much more satisfactory with fresh material than with fixed. Spicules were isolated by boiling portions of the specimens in caustic potash. All material for sectioning was fixed in alcohol or corrosive sublimate. Bleaching of the zooids was necessary in many of the compound forms and was carried out by the Mayer chlorine method (Bolles Lee, 10th Edit., p. 254). Hydrochloric acid carmine was found to be the most useful stain.

List of Species Described.

Synoicidae.

1.

Aplidium thomsoni n.sp. (X)

2.

Aplidium (Amaroucium) adamsi n.sp. (X)

3.

Aplidium (Amaroucium) phortax Michaelsen

4.

Aplidium (Amaroucium) benhami n.sp. (X)

Didemnidae.

5.

Didemnum psammatodes (Sluiter) var. maculatum (Nott)

6.

Didemnum candidum Savigny

7.

Diplosoma macdonaldi Herdman (X)

Polycitoridae.

8.

Polycitor (Eudistoma) circumvallutum (Sluiter)

9.

Distaplia fasmeriana Michaelsen

Ascidiidae.

10.

Ascidia aspersa (Müll.) (X)

Rhodosomatidae.

11.

Corella eumyota Traustedt.

Bofryllidae.

12.

Botryllus leachi Savigny

13.

Botryllus schlosseri (Pallas)

Styelidae.

14.

Asterocarpa cerea (Sluiter)

15.

Cnemidocarpa bicornuata (Sluiter)

Pyuridae.

16.

Pyura subuculata (Sluiter)

17.

Pyura cancellata n.sp. (X)

18.

Pyura pulla (Sluiter)

19.

Pyura pachydermatina (Herdman)

Species marked (X) in the above list are those not hitherto recorded from New Zealand.

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Description of Species.

Explanation of Lettering.
av. atrial velum
dl. dorsal lamina
dt. dorsal tubercle
ecp. endocarp
g. gonad
gc. gastric caecum
ilv. internal longitudinal vessel
in. intestine
ing. intestinal gland
ip. incubatory pouch
l. “liver”
lv. larva
ng. neural gland
oe. oesophagus
po. “problematical organs”
r. rectum
rc. renal cells
re. reservior
sd. sperm duct
so. “Seitenorgane”
st. stomach
up. umbilical process
vp. vascular process
ovary
testis

Order Krikobranchia Seeliger.

These arc compound ascidians having the body divided into two or three distinct parts or segments (thorax, abdomen, and sometimes post-abdomen), the digestive tract and reproductive organs being situated in the posterior part or parts of the body. The tentacles are simple; the branchial sac is without folds or internal longitudinal vessels.

Family Synoicidae Hartmeyer.

The body is composed of three divisions, the last (post-abdomen) containing the reproductive organs and heart. Budding occurs by segmentation of the post-abdomen.

Genus Aplidium Savigny.

This genus was revised by Van Name in 1921 and now includes both the genus Aplidium and the genus Amaroucium Milne-Edwards, 1841. It is defined as follows: The post-abdomen (when fully developed) is elongate and is not separated from the abdomen by an elongate neck, though there may be a slight constriction between these two parts of the body. The post-abdomen may be very short when the reproductive organs are not well developed. The stomach usually has distinct longitudinal plications; an atrial languet is present in most forms, but may be absent.

Subgenus Aplidium.

Members of this subgenus are distinguished by having the branchial sac short, with few (commonly five to ten) rows of stigmata, the post-abdomen short, the atrial aperture back from the anterior end of the thorax and often without a languet, and the testis lobes in a more or less compact group instead of in an elongated series.

Aplidium thomsoni n.sp. (Text-fig. 1; Plate 3, Fig. 2.)

This species forms small rounded colonies on the under-surfaces of rocks and on the internodes of Hormosira banksii (Turn.) just below high water level in all three localities. The colonies are orange in colour with zooids arranged in small stellate systems, but coloration and zooid arrangement are partly masked by the fine sand grains impregnated throughout the test. The largest colony measured 3.9 cm. in the longest diameter. The height above the substratum varies from

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2 to 9 mm., being usually greater in the central region of the colony. There is no tendency to mound formation around the common cloacal apertures, which are extremely small and separated by distances of 3 to 7 mm. The test is composed of a firm, light orange, transparent substance and contains many small test cells. Orange pigment is present in all parts of the zooids, being most concentrated in the ova, which appear reddish in hue.

Zooids measure up to 5 5 mm. in length and 0.5 mm. in width in the pharyngeal region and are charterised by a narrow post-abdomen occupying one half of the body length. Six short triangular lobes surround the branchial aperture. The atrial aperture is surmounted by a single lappet with two short side branches near the distal end. The wall of the pharynx is broken by five rows of twelve to fifteen stigmata, eight to ten times as long as they are broad. Longitudinal muscles pass obliquely down the pharynx to the end of the post-abdomen, where there is a tendency to concentration on the ventral side. This peculiar disposition of the muscles fibres in the post-abdomen is, according to Michaelsen, also characteristic of A. appendiculatum Mich., A. scabellum Mich., and A. circumvollutum (Sluit.). Three or four transverse muscle fibres are present between the rows of stigmata. Branchial tentacles are sixteen in number and belong to three orders of size. The dorsal lamina i composed of five short curved languets which curve backwards at the level of the first slit from the mid-dorsal line. The oesophagus is short and leads to a short rounded stomach with five or six longitudinal folds. The intestine passes backwards for a short distance before it turns to run up towards the atrial aperture, and in the majority of specimens there is a slight constriction near the beginning of the ascending loop.

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Text Fig. 1.—Aplidium thomsoni. Right side of zooid. × 20.

The testis extends through almost the entire post-abdomen. It is composed of ten to eighteen lobes irregularly arranged around the sperm duct, which runs straight up towards the atrial aperture. The ovary lies in between the testis blocks about one-third of the way down the post-abdomen. Tadpoles (Plate 3, Fig. 2) are deep orange in colour and were present in the mantle cavities of specimens collected between the beginning of September, 1944, and the end of April, 1945 The largest tadpole measured 2.7 mm. in length and 0.6 mm. in width in the head region.

Distribution: Otago Harbour.

Remarks: It is interesting to note that specimens from coastal rocks at North Cape and from 35 fathoms in the Colville Channel described and figured by Michaelsen (1924, pp. 383388) under the name Amaroucium circumvollutum (Sluiter) resemble badly fixed specimens of Otago material in the general shape, in the concentration of longitudinal muscles on the ventral side of the post-abdomen, and

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in the number of stomach folds (five, Michaelsen). Amaroucium circumvollutum is described by Sluiter as having fourteen rows of small rounded stigmata in the pharynx. Michaelsen's material was badly fixed and he gives no detailed description of the pharynx. There is the possibility that, as in A. thomsoni, a comparatively long pharynx may contain but few rows of stigmata, and that Michaelsen's specimens have been wrongly identified.

The only other species recorded from the New Zealand geographical region that might belong to the sub-genus Aplidium is Amaroucium foliaceum, which differs from the Otago species in the number of rows of pharyngeal stigmata, the number of stigmata per row, and the number of folds in the stomach wall, nor can the author find any species recorded from the Australian or the South Polar regions with which the Otago species is identical. The specific name is given in compliment to the late Mr. G. M. Thomson, to whom the Portobello Marine Biological Station is much indebted.

Type Specimen: Otago Museum.

Subgenus Amaroucium (Milne-Edwards).

This subgenus is distinguished from the subgenus Aplidium by having zooids with a more elongate branchial sac and post-abdomen, and the atrial aperture placed well forward near the anterior end of the pharynx. The atrial languet is always present. The rows of stigmata are numerous; the testis lobes are arranged along the sperm duct in an elongate single or double series.

Aplidium (Amaroucium) phortax Michaelsen. (Text Fig. 2; Plate 3, Fig. 4.)

For Synonymy and Literature see: 1924, Amaroucium phortax Michaelsen, Vidensk. Medd. naturh. Foren., bd. 77, pp. 389400.

This species forms large fleshy masses on the under-surfaces of rocks, on wharf piles, etc., in all three localities. The colonies are usually white, but pale yellow and grey forms also occur. The largest colony measured was 10 cm. in the longest diameter. The height above the substratum varies from 1.5 to 2 0 cm. and there is no tendency to mound formation around the common cloacal apertures, all marked unevennesses of the surface being due to the contour of the underlying substratum. The common cloacal apertures are inconspicuous (from 0.3 to 0 6 mm. in the longest diameter), and as even in living colonies the zooids appear to be most irregularly arranged and few faecal pellets are seen in the common cloacal canals no clear picture can be given of the distribution of the zooids around the common cloacal apertures. The test is firm, transparent, and either colourless or faintly diffused with pigment. Small test cells and a few large round cells are present throughout the test, but the “Sternchenzellen” described by Michaelsen were not seen. Upon fixation in formalin the test becomes firmer in consistency and changes colour, becoming light or dark grey—as Michaelsen describes it—“mausgrau oder sehr hell gelblich grau”. Michaelsen records in addition some colourless specimens among his fixed material. The stomach of the zooids and the ripe eggs are yellow, and in the yellow colonies this pigment is present also in the pharynx and the test.

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The zooids are extremely contractile and only a few fully expanded ones were obtained. They measure up to 11 mm. in length and 0.7 mm. in width in the pharyngeal region and are characterised by a narrow post-abdomen occupying two-thirds of the body length. Six short triangular lobes surround the branchial aperture. The atrial aperture is surmounted by one or two small strongly-built muscular lappets. The wall of the pharynx is broken by twelve or thirteen rows of ten or eleven stigmata, three or four times as long as they are wide. Thirteen or fourteen bundles each containing two or three longitudinal muscle fibres run down the pharynx wall and continue right down into the post-abdomen, but show no tendency towards concentration on any side of the zooid. Three to six tranverse muscle fibres are present between the rows of stigmata. Branchial tentacles are sixteen in number and belong to at least two orders of size. The dorsal lamina is composed of twelve or thirteen long languets which curve back at the level of the third or fourth stigmata from the dorsal edge. The oesophagus is short and leads to a short rounded stomach with twenty-three to twenty-six longitudinal folds. The intestine continues backwards for a short distance before turning to run up towards the atrial aperture. In expanded zooids there are no marked constrictions of the intestinal wall, such as are figured by Michaelsen (1924, p. 393, Fig. 21a.)

The testis extends throughout the posterior half of the post-abdomen and consists of fifty-four to seventy-four lobes arranged in two parallel rows around the sperm duct, which runs straight up towards the atrial aperture. The ovary lies in the anterior half of the post-abdomen, a short distance in front of the most anterior testis lobes. Tadpoles undergo development within the mantle cavity in a type of brood pouch, the shape of which depends on the number of tadpoles present, and can hardly be used as a distinguishing feature, though Michaelsen gives it a certain amount of prominence in this species. Tadpoles (Plate 3, Fig. 4) are light yellow and were present from the middle of November, 1944, until the end of March, 1945. The largest tadpole measured 2 9 mm. in length and 0.9 mm. in width in the head region.

Distribution: In New Zealand—f. typica—Tauranga (Mich.), d'Urville Island (Sluit.), Otago Harbour; var. ptychodes Mich.—Stewart Island (Mich.) Elsewhere—f. typica—Chatham Islands (Sluit.).

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Text Fig. 2.—Aplidium (Amaroucium) phortax. Right side of zooid. × 25.

Remarks: Although type specimens are not available, the differences between the description given above and Michaelsen's

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description of A. phortax f. typica are such minor ones that the author feels justified in placing the Otago specimens in this species. The differences noted in the structure of the pharynx are probably due to the fact that more specimens were available in Otago, for in almost every case Michaelsen's figures come within the range given above, the exceptions being the number of stigmata per row (9, Michaelsen; 10 to 11, Otago specimens) and the number of branchial tentacles. However, as Michaelsen admits that the inner organisation of the thorax cannot be clearly stated due to the strong contraction of the zooids, these factors can be discounted. The only other difference is the absence of “Sternchenzellen” in the test. So far, var. ptychodes has not been seen in the Otago Harbour.

Aplidium (Amaroucium) adamsi n.sp. (Text Fig. 3; Plate 2, Fig. 4; Plate 3, Fig. 1.)

This species forms large fleshy masses on the under-surfaces of rocks, wharf piles, etc., in all three localities. The colonies are usually bright pink or orange in colour, but pale yellow and light pink specimens are also found. The largest colony measured was 15 cm. in the longest diameter. The height above the substratum ranges from 10 to 14 mm. at the edge of the colony to 25 to 35 mm. at the common cloacal apertures. Unevennesses of the surface are due primarily to mound formation around the common cloacal apertures, which are large (up to 5 mm. in the longest diameter), and are separated by distances of 0 9 to 1.8 cm. The zooids are arranged in irregular branching systems (Plate 2, Fig. 4.) The test is colourless, semi-transparent, of a soft gelatinous consistency, and undergoes no marked changes upon fixation in formalin. Throughout the entire test numerous small test cells and a few large round cells are present, and in the surface layers many white spicule-like structures are also found. These are rosette-like in appearance, 0.7 to 0 8 μ in diameter, and give no reactions when treated with acids or alkalis. The zooids have a brilliantly coloured pharynx, a pale yellow abdominal region, and a post-abdomen which is colourless except for the ovary, in which the ripe eggs are deep maroon.

Zooids measure up to 28 mm. in length and 1 0 mm. in width in the pharyngeal region and are characterised by a narrow post-abdomen occupying two-thirds of the body length. Six short triangular lobes guard the branchial aperture. The atrial aperture is surmounted by one or two long, wide lappets in which muscle fibres are very poorly developed or entirely lacking. The wall of the pharynx is broken by twelve or thirteen rows of nine or ten stigmata, four or five times as long as

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Text Fig. 3.–Aplidium (Amaroucium) adamsi. Right side of zooid. × 20.

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they are broad. Thirteen or fourteen bundles each containing one or two muscle fibres run down the pharynx wall and continue down into the post-abdomen, but show no tendency to concentration on any one side of the zooid. Three or four transverse muscle fibres are present between the rows of stigmata. Branchial tentacles are sixteen in number and belong to three orders of size. The dorsal lamina is composed of twelve or thirteen long langucts which curvé backwards at the level of the third or fourth stigmata from the dorsal edge. The oesophagus is short and leads to a short rounded stomach with twenty-two to twenty-four longitudinal folds. The intestine passes backwards for a short distance before turning to run up towards the atrial aperture. There are no marked constrictions of the intestinal wall.

The testis extends throughout the posterior three-quarters of the post-abdomen and consists of forty-six to fifty-six lobes arranged in two parallel rows around the sperm duct, which runs straight up towards the atrial aperture. The ovary lies in the anterior quarter of the post-abdomen, a short distance in front of the most anterior testis lobes. Tadpoles undergo development within the mantle cavity and the shape of the pouch so formed depends entirely on the number of tadpoles present. Tadpoles (Plate 3, Fig. 1) are bright orange and were present from the beginning of November, 1944, until the end of March, 1945. The largest tadpole measured 4 3 mm. in length and 1.1 mm. in width in the head region.

Distribution: Otago Harbour.

Remarks: This species is distinguished from A. (A.) phortax f. typica by:—

(1)

Mound formation around the common cloacal apertures.

(2)

The test is of softer consistency and undergoes no marked changes upon fixation in formalin.

(3)

The lower powers of contractility of the zooids.

(4)

The structure of the atrial lappets.

(5)

The size and colour of the tadpoles.

Added to that, although colour varieties of the two species are found in Otago Harbour, the fact that no intermediate forms occur marks them clearly as two different species.

This species is distinguished from A. (A.) phortax var. ptychodes by:—

(1)

Mound formation around the common cloacal apertures.

(2)

The absence of pigment in the test.

(3)

The size of the colonies.

From a survey of the literature of the genus the author can find no species with which it is identical and has decided to name it Aplidium (Amaroucium) adamsi after Mr. W. Adams, who has been associated with the Portobello Marine Biological Station for many years.

Type Specimen: Otago Museum.

Aplidium (Amaroucium) benhami n.sp. (Text Fig. 4; Plate 2, Figs. 1, 4; Plate 3, Fig. 3; Plate 5, Fig. 1.)

This species forms small colonies on the under-surfaces of rocks and on the fronds and holdfasts of seaweeds in all three localities. The colonies are very conspicuous on account of the brilliant orange coloration and the stellate arrangement of the zooids (Plate 2, Figs.

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1, 4). The test is free from sand grains. The largest colony measured 4.5 cm. in the longest diameter. The height above the substratum varies from 5 to 8 mm., but is almost uniform within the one colony. Common cloacal apertures are small (1.0 to 2.0 mm. in the longest diameter) and are separated by distances of 4.0 to 6.0 mm. They form the outlet for ten to eighteen zooids which are arranged around them in stellate or elongate oval patterns. The test is firm, orange, transparent, and contains many small test cells and a few large round cells, the latter being confined to the surface layers. In formalin the colonies fade to a dirty white and the arrangement of the zooids is lost. Orange pigment is present in all parts of the zooids. being concentrated in the eggs, and partly masked by an additional white pigment in the pharyngeal region.

Zooids measure up to 8 mm. in length and 0.9 mm. in width and are characterised by a wide post-abdomen (up to 0.65 mm. in width) occupying approximately one-half of the length of the zooid. Six short triangular lobes surround the branchial aperture. The atrial aperture is surmounted by three long, well-developed lappets, the central one of which is slightly longer than the others. The wall of the pharynx is broken by ten or eleven rows of fourteen to sixteen stigmata, five to seven times as long as they are wide. Bundles of not more than two longitudinal fibres run down the pharynx wall, but are not concentrated on any one side of the zooid. Three to five transverse muscle fibres are present between the rows of stigmata. Branchial tentacles are sixteen in number and belong to three orders of size. The dorsal lamina is composed of ten or eleven long languets which curve backwards at the level of the fourth or fifth stigmata from the dorsal edge. The oesophagus is comparatively longer than that of A. (A.) phortax and A. (A.) adamsi. It leads to a short rounded stomach with twenty-two to twenty-six longitudinal folds. The intestine passes backwards for a short distance before turning to run up towards the atrial aperture. There are no marked constrictions of the intestinal wall.

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Text Fig. 4.—Aplidium (Amaroucium) benhami. Right side of zooid. × 25.

The testis extends throughout the posterior two-thirds of the post-abdomen and consists of twenty-eight to forty-two lobes arranged around the sperm duct, which runs straight up towards the atrial aperture. The ovary lies in the anterior third of the post-abdomen directly in front of the most anterior testis lobes. Tadpoles (Plate 3, Fig. 3) are bright orange and were present in the mantle cavities of specimens collected between the middle of November, 1944, and the end of February, 1945. The largest tadpole measured 3.4 mm. in length and 0 63 mm. in width in the head region.

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Distribution: Otago Harbour.

Remarks: From a careful survey of the literature of this genus it is apparent that the species described above is not identical with any previously described from the New Zealand geographical region. It most closely resembles A. (A.) multiplicatum (Sluiter) recorded from the Phillipines and the Malay Archipelago, but is distinguished from it by the number of atrial lappets and the size and form of the colony. The specific name is given in compliment to Professor Sir W. B. Benham, K.B.E.

Type Specimen: Otago Museum.

Family Didemnidae Verrill.

These are compound ascidians with minute zooids, having the body divided by a constriction into two parts (thorax and abdomen). The branchial sac has only three or four rows of stigmata. Didemnidae have a peculiar method of budding by which each new individual grows from two buds (one from the thorax and one from the abdomen), arising near the constricted middle portion of the body, so that the characteristic double zooids with the two individuals joined together by the middle part of the body are temporarily found.

Genus Didemnum Savigny.

There are four rows of stigmata in the branchial sac. The proximal part of the sperm duct is wound spirally about the testis. Calcareous spicules are present in the test.

Didemnum psammatodes (Sluiter) var. maculatum (Nott). (Text Fig. 5; Plate 3, Fig. 5; Plate 4, Fig 11.)

For Synonymy and Literature see: 1924, Didemnum psammatodes var. maculatum, Michaelsen, Vidensk. Medd. naturh. Foren., bd. 77, p. 341.

This species forms smooth leathery irregularly-shaped masses on the under-surfaces and sides of rocks in all three localities. The colonies are black, dark purple, Indian red, light brown or grey, and are very conspicuous because of the white edging around the branchial and common cloacal apertures and the outer edge of the colony itself. The largest colony measured 14 cm. in the longest diameter. The height above the substratum varies from 2.0 to 3.2 mm., and is almost uniform in the one colony. Common cloacal apertures are slit-like (0.5 to 0 7 mm. in the longest diameter) and are separated by distances of 3 to 19 mm. The zooids are 0 5 to 1.0 mm. apart and are not arranged in definite systems. Extensive common cloacal canals are present and separate the test into two regions, an upper (occupying one-tenth of the height above the substratum) which is pigmented and contains numerous bladder and a few test cells, and a lower (occupying nine-tenths of the height above the substratum) which is non-pigmented and contains very few bladder and numerous test cells. Spicules are present in all parts of the lower region, but in the upper region they are confined to small areas around the branchial and common cloacal apertures, to the edge of the colony, and to a narrow band roofing the common cloacal canals. The degree of spiculation varies in different colonies, and the spicules vary in size in the one colony. Spicules are 0 007 to 0.032 mm. in diameter and are of the spherical stellate type shown in Plate 4, Fig. 11. In formalin the

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colonies fade to a dirty white. The zooids are yellow with deeper pigmentation in the abdominal region. The common cloacal canals are inhabited by commensal amphipods and other crustacea.

Zooids measure up to 3 mm. in length and 0.5 mm. in width in the pharyngeal region. The rectal-oesophageal region is long (one and a-half times the length of the pharynx), and the posterior region of the abdomen is wide (up to 0.9 mm.). The branchial siphon is long and is surmounted by six small triangular lobes. There is no atrial lappet. The wall of the pharynx is broken by four rows of seven to nine stigmata. Branchial tentacles are very small, but there appear to be about thirty belonging to three different orders of size. The dorsal lamina is composed of four curved languets. The oesophagus is long and narrow and leads to a short, smooth-walled stomach. The intestine takes two almost right-angled turns and runs up towards the atrial aperture without any marked constrictions. There are no external intestinal glands. From the central narrow portion of the zooid project two lobed “Seiten-organe” and a long muscular process.

The testis is large and unlobed. The sperm duct takes eight or nine spiral turns before passing straight up towards the atrial aperture. The ovary lies between the testis and the stomach. Tadpoles (Plate 3, Fig. 5) are yellow and were present in the cloacal canals between the beginning of January, 1945, and the middle of February, 1945. The largest tadpole measured 4.4 mm. in length and 1.1 mm. in width in the head region.

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Text Fig. 5.—Didemnum psammatodes var. maculatum. Left side of zooid. × 40.

Distribution: In New Zealand—Auckland Harbour (Nott), Bay of Islands (Mich.), Otago Harbour. Elsewhere—Mozambique (Sluit. and Mich.).

Remarks: Spicules are known to be very varied in shape within a single species of Didemnum and in all other respects the Otago specimens are identical with those described by Nott (1892) as Leptoclinum maculatum. Michaelsen (1924) considered Nott's species to be but a variety of Didemnum psammatodes, hence the Otago specimens are described above under the name of Didemnum psammatodes var. maculatum.

Didemnum candidum Savigny. (Text Fig. 6; Plate 3, Fig. 7; Plate 5, Fig. 1; Plate 4, Fig 10.)

For Synonymy and Literature see: 1924, Didemnum candidum, Michaelsen, Vidensk. Medd. naturh. Foren., bd. 77, pp. 358, 359.

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Didemnum candidum is the inost common compound ascidian in the vicinity of the Portobello Marine Biological Station and occurs under rocks, on wharf piles, and on the branches of Hormosira banksii (Turn.) and Cystophora torulosa (R. Br.) in all three localities, flourishing even in muddy situations intolerable to other compound species. White, fawn, and light pink forms are found. The largest colony measured 18 cm. in the longest diameter. The height of the colony depends mainly on the type of substratum, colonies growing on hard rock surfaces being thin (1.0 to 2.5 mm. in thickness), whereas those growing on soft surfaces, e.g., sponges and hydroids, tend to become cancellous and reach thicknesses of up to 12 mm. In colonies with dense spiculation the surface is rough and branchial and common cloacal apertures are difficult to distinguish, but in colonies with a lower degree of spiculation the surface is smooth and the branchial and common cloacal apertures are quite apparent, the latter being 0.5 to 1.0 mm. in diameter and separated by distances of 1 0 to 2.0 cm. In a few colonies the zooids can be seen to be arranged around the common cloacal apertures in irregular branching systems. Numerous large bladder and small test cells are found throughout the test, as is also any pigment present. Spicules are 0.019 to 0.027 mm. in diameter and are of the spherical stellate type shown in Plate 4, Fig. 10. In a single colony spicules may be strikingly uniform or may vary considerably in size, or in occasional cases may vary both in size and shape. Neighbouring colonies may differ considerably in the type and average size of their spicules. Zooids are yellow with deeper pigmentation in the abdominal region.

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Text. Fig. 6.—Didemnum candidum. Left side of zooid. × 50.

Zooids measure up to 2.0 mm. in length and 0.6 mm. in width in the pharyngeal region. The length of the rectal-oesophageal region does not exceed that of the pharynx, and the posterior end of the abdomen is slightly wider than the pharynx. The branchial siphon is much shorter than that of Didemnum psammatodes and is surmounted by six triangular lobes, the size of which varies in different colonies. There is no atrial lappet. The wall of the pharynx is broken by four rows of eight to twelve narrow stigmata. Branchial tentacles are sixteen in number and belong to three orders of size. The dorsal lamina is composed of four curved languets. The oesophagus is short and narrow and leads to a short, round, smooth-walled stomach. The intestine takes two almost right-angled turns and runs straight up towards the atrial aperture without any marked constrictions. A much-branched intestinal gland surrounds the lower portion of the ascending loop. From the narrow central region of the zooid project two small “Seitenorgane” and a muscular process, often of considerable length.

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The testis is either undivided or separated into two or occasionally three lobes. The sperm duct takes six to eight spiral turns before passing straight up towards the atrial aperture. The ovary lies between the testis and the stomach. Small white tadpoles (Plate 3, Fig. 7) were present in the cloacal canals between the beginning of November, 1944, and the end of December, 1944. The largest tadpole measured 2.7 mm. in length and 0.55 mm. in width in the head region.

Distribution: In New Zealand—Auckland Harbour (Nott), Hauraki Gulf, Colville Channel, Queen Charlotte Sound, Lyttelton. Stewart Island (Mich.), Otago Harbour. Elsewhere—East Coast of America from New Hampshire to Bahia (Herdman and Van Name), Magellan Region (Herdman and Mich.), Mozambique (Sluiter), South Madagascar and Mauritius (Mich.), Red Sea (Savigny), Philippines (Herdman), Great Barrier Reef (Hastings), Indian Ocean (Mich.).

Genus Diplosoma MacDonald.

In this genus are four rows of stigmata; the testis is divided into two separate glands, and the sperm duct is not spirally coiled. No atrial languet or atrial tube is developed and the test is without spicules. Usually the common cloacal apertures are greatly developed.

Diplosoma macdonaldi Herdman. (Text Fig. 7; Plate 3, Fig. 6.)

For Synonymy and Literature see: 1930, Diplosoma macdonaldi, Van Name, New York Acad. Sci., vol. 10, pt. 4, p. 440.

This species forms thin, irregularly-shaped colonies on the branches of Cystophora torulosa (R. Br.) and Hormsosira banksii (Turn.) and occasionally on the under-surfaces of rocks just below low water mark in all three localities. The colonies are khaki or yellow in colour, depending on the amount of black pigment present in the mantle wall. The height above the substratum rarely exceeds 3 mm., but the test around the common cloacal apertures is drawn out into long thin tubes up to 1 0 cm. in length. Common cloacal apertures are 1.0 to 1.5 cm. apart and serve as the outlet for very extensive common cloacal canals. The zooids are not arranged in definite systems and in some parts of the colony may be closely crowded, whilst in other parts they may be separated by distances of up to 8 mm. The test is smooth, semi-transparent, and without spicules. Numerous large bladder cells and small test cells are present throughout the test, and in the surface layers patches of small cream cells, which give the test a milky appearance in living colonies, are also found. The zooids are yellow or orange with varying amounts of black pigment in the mantle wall. When colonies are placed in formalin the tubes bearing the common cloacal apertures are withdrawn and the milky appearance of the test is lost.

Zooids measure up to 1.6 mm. in length. The rectal-oesophageal region is short and the posterior region of the abdomen is the same width as the pharynx. Although the branchial aperture appears in surface view to be without lobes, six small triangular ones are obvious in sections and whole mounts. There is no atrial lappet. The wall of the pharynx is broken by four rows of nine to ten stigmata. Branchial tentacles are twelve to sixteen in number and are of at least two orders of size. The dorsal lamina is composed of four curved languets.

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The oesophagus is short and leads to a short, round, smooth-walled stomach. The intestine takes a wide curve before turning to run up towards the atrial aperture. There are no marked constrictions and no external intestinal glands.

Two large testis lobes are present and a wide sperm duct passes from them straight up to the atrial aperture. The ovary occupies a median position in the abdominal dilatation. Small, light orange tadpoles (Plate 3, Fig. 6) were present in the common cloacal canals between the end of December, 1944, and the end of February, 1945. The largest tadpole measured 2.7 mm. in length and 0.6 mm. in width in the head region.

Distribution: In New Zealand—Otago Harbour, and also collected by the author in Auckland Harbour, December, 1944. Elsewhere—East Coast of America from Bermuda and South Carolina to Bahia (Herdman and Van Name), Florida, West Indies (Harymeyer), Malayan Region (Gottschaldt and Van Name).

Remarks: No species of Diplosoma have been recorded previously from New Zealand, the Chatham or the Auckland Islands, and only two very doubtful species from Australia, D. rayneri MacDonald, 1858, and D. spongiforme (Giard) var.?, Michaelsen, 1930. The Otago specimens are identical with those described from the Philippines (1918) and from the West Indies (1921, 1930) by Dr. Van Name as Diplosoma macdonaldi, and it is possible that this species like Didemnum candidum is a very widely distributed one.

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Text Fig. 7—Diplosoma macdonaldi. Left side of zooid. × 65.

Family Polycitoridae Hartmeyer.

Compound ascidians having the body consisting of two parts (thorax and abdomen) joined by a constricted part or neck usually rather long. The buds form on vascular processes or stolons (often of considerable length) arising from the posterior end of the abdomen of the parent. Dorsal lamina represented by separate languets. Reproductive organs in the abdomen (or in a diverticulum of it) on or near the loop formed by the intestine.

Genus Polycitor Renier.

This genus according to Hartmeyer, 1909, includes both the genus Polycitor Renier and the genus Eudistoma Caullery. Van Name, 1930, defined it as follows: Colonies massive, mostly cushion-forming, but may be stalked. Systematic arrangement of zooids and common cloacal apertures mostly lacking. Body openings each with six lobes. Brood pouch not present. The genus includes forms with many rows of stigmata, and a plicated stomach wall (constituting the sub-genus Polycitor) and those with but three or four rows of stigmata and

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a globular stomach, always smooth-walled, which constitutes the sub-genus Eudistoma.

Polycitor (Eudistoma) circumvallatum (Sluiter). (Text Fig. 8; Plate 3, Fig. 8.)

Synonymy: 1900, Distoma circumvallata Sluiter, Zool. Jahrb. Syst., 13, pp. 89, Taf. 1, Fig. 4, Taf. 2, Fig. 6. 1909, Polycitor (Eudistoma) circumvallatum (Sluit.) Hartmeyer, Bronn's Klassenu-Ordnungen Thier-Reichs, p. 1431. 1924, Eudistoma circumvallata (Sluit.) Michaelsen, Vidensk. Medd. naturh. Foren., bd. 77, p. 285.

Clusters of small, white, flat-topped colonies of this species occur on the sides and under-surfaces of rocks betwen tide marks at the Portobello Point, but so far no specimens have been found at Goat Island or Quarantine Island. The colonies are almost circular in outline with fairly abrupt sides tapering gradually towards the base. The surface of the colony varies from 0.5 to 4.8 cm. in width, and the height above the substratum ranges from 1 0 to 2.0 cm., but is almost uniform in the one colony. The zooids are not arranged in systems and there are no common cloacal apertures. The test is colourless, transparent, of a soft, gelatinous consistency, and contains numerous small test cells and a few bladder cells. Yellow pigment occurs in all parts of the zooids and is concentrated in the ripe eggs. In formalin the test changes to olive green and the zooids fade to white.

The zooids are extremely contractile and only a few fully expanded ones could be obtained. They measure up to 1.2 cm. in length and 1.0 mm. in width in the pharyngeal region. The rectal-oesophageal region is long and narrow and the width of the posterior region of the abdomen is equal to that of the pharynx. The atrial siphon is longer than the branchial siphon and both bear six short lobes at the distal end. The wall of the pharynx is broken by three rows of seven to nine stigmata, five or six times as long as they are wide. Eight or nine bundles of five or six longitudinal muscle fibres are present in the mantle wall and twenty bundles of two or three transverse muscle

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Text Fig. 8.—Polycitor (Eudistoma) circumvallatum. Left side of zooid. × 33.

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fibres surround the pharyngeal region. Branchial tentacles are twenty-five to thirty-two in number and are arranged in two rows. The dorsal lamina is composed of three long narrow languets. The oesophagus is extremely long (Text Fig. 8) and passes directly back to the stomach—a dome-shaped, smooth-walled structure situated towards the posterior end of the zooid. The intestine is narrow, curves almost immediately after leaving the stomach, and then runs straight up to open near the base of the atrial siphon. There are no external intestinal glands.

The reproductive organs lie in the curve of the intestinal loop. The testis consists of twelve to eighteen large lobes from which a long sperm duct runs up towards the atrial siphon. The ovary occupies a median position in the abdominal dilatation. There is no definite structure set aside as a brood pouch. Tadpoles (Plate 3, Fig. 8) are light yellow and were present in the mantle cavity between the middle of November, 1944, and the end of January, 1945. The largest tadpole measured 2.2 mm. in length and 0.5 mm. in width in the head region.

Distribution: D'Urville Island (Sluiter), Otago Harbour.

Remarks: Sluiter's description of the type specimen is by no means complete, but as type specimens are not available and the Otago specimens very closely resemble the d'Urville Island ones, the author feels justified in including them in the same species.

Genus Distaplia Della Valle.

The branchial sac has four rows of stigmata, each row crossed at its middle by a slender transverse (dorso-ventral) vessel. Development of the embryos (in typical species, at least) takes place in a large pouch or external diverticulum of the peribranchial cavity into which the oviduct passes.

Distaplia fasmeriana Michaelsen. (Text Fig. 9; Plate 2, Fig. 1; Plate 3, Fig. 9; Plate 5, Fig. 2.)

Synonymy: 1924, Distaplia fasmeriana Michaelsen, Vidensk. Medd. naturh. Foren., bd. 77, p. 297.

Clusters of purple club-shaped colonies of this species form conspicuous masses on rocks near and below low water mark at the Portobello Point, but so far no specimens have been found at Goat Island or Quarantine Island. The colonies are stalked. The stalk is slightly shorter and narrower than the head region and is built up mainly of test substance which is light brown in colour. Numerous branchial apertures each edged with bright purple pigment open on the head region of the colony, and render this region very conspicuous. Common cloacal canals are confined to the head region of the colony and are usually more numerous towards the distal end. They are slit-like, measuring up to 0.3 mm. in the longest diameter. The zooids are arranged around them in irregular branching systems, the branches of which have a tendency to extend radially towards the proximal end of the head region (Plate 2, Fig. 1). Colonies range from 1.6 to 5.0 cm. in the combined length of head and stalk, and from 0.5 to 5.0 cm. in the width of head. The test is light brown, semi-transparent, and contains numerous small test cells, round bladder cells, and pigment cells. The mantle of the zooids is splashed with bright purple pigment, and purple pigment is also present in

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the pharyngeal region and in the long vascular processes extending from the posterior ends of the zooids. The stomach and intestine are

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Text Fig. 9.—Distaplia fasmeriana. Left side of zooid (A) as in June, (B) as in September and October.

yellow and traces of yellow are sometimes seen around the branchial apertures. Commensal amphipods are found in the common cloacal apertures.

Zooids measure up to 2 mm. in length (not including the vascular processes, which in some cases reached 10 mm. in length) and 1.2 mm. in width in the pharyngeal region. The rectal-oesophageal region is very short and the abdominal region is slightly narrower than the pharyngeal. Six short triangular lobes surround the branchial aperture. The atrial aperture is smooth-edged and has the anterior lip produced into a long lappet. (The other types of atrial aperture described by Michaelsen were not seen.) The wall of the pharynx is broken by four rows of ten to twelve stigmata, four or five times as long as they are wide, and each is crossed by a fine parastigmatic vessel. A few widely-separated longitudinal muscle fibres run obliquely down the zooid. Four or five transverse muscle fibres are present between the rows of stigmata. Branchial tentacles are sixteen in number and of three orders of size, regularly arranged. The dorsal lamina is composed of four long narrow languets. The oesophagus is

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short and leads to a wide curved stomach, which is wider at the anterior end than at the posterior end. The stomach wall is thrown into fourteen to eighteen longitudinal folds. The intestine is divided into two regions, a short narrow region near the stomach, and a somewhat wider posterior region. (Note: Michaelsen figures four regions in the intestine. The appearance of these may have been due to contraction of the zooids.) The reservoir of the intestinal gland is a round structure situated between the stomach and the recurved portion of the intestinal loop.

Reproductive organs are contained in a sac which projects into the anterior portion of the vascular process of the zooid, and in 1944 were discernable for a short period of the year only, from May to September. The testis is composed of eight to fourteen lobes. The sperm duct is wide and runs straight up towards the atrial aperture. This duct was found to be distended with sperms in specimens collected in June and July. The ovary was discernable in specimens collected in June and contained but a single egg. Testis lobes had disappeared by the end of September. A brood pouch to house the one developing embryo arises as an outpushing of the mantle at a point on the dorsal side of the zooid level with the base of the pharynx. This swells to a bladder-like structure and remains attached to the zooid by a long narrow stalk. Measurements of a brood pouch containing an almost fully-developed embryo are: bladder, 2 mm. long, 1.5 mm. wide; stalk, 1.4 mm. long, 0.3 mm. wide. Budding takes place in the embryo, which remains attached to the brood pouch by a peculiar type of umbilical process (Plate 3, Fig. 9) until it is fully developed. The tadpole escapes by breaking through the wall of the brood pouch and through the surface of the over-lying test. Tadpoles (Plate 3, Fig. 9) are large cream structures, and in 1944 were liberated in November only. The largest measured 6.8 mm. in length and 1.6 mm. in width in the head region.

Distribution: Stewart Island (Michaelsen), Otago Harbour.

Remarks: The specimens described above obviously belong to the same species as those specimens described from Stewart Island by Michaelsen, 1924, and the author has collected this species at Stewart Island. Michaelsen's specimens were collected in November, when brood pouches were well developed but no sex organs were apparent.

Note: The position of the sex organs is rather peculiar in this species. In the majority of species belonging to this genus in which gonads are held in a sac outside the intestinal loop, the sac stands free from the zooid, as, for example, in D. bursata (Van Name). In D. fasmeriana, however, they lie in a sac in the anterior portion of the vascular process, giving the zooid the appearance of a member of the Synoicidae. The short period for tadpole production is worthy of note, as is also the fact that only one egg is produced per zooid. Both these facts indicate a high degree of specialisation and justify the systematic position of the genus Distaplia at the top of the Krikobranchiata.

Order Diktyobranchia Seeliger.

This is a rather well-defined, though varied, group of simple and compound ascidians having a system of internal longitudinal vessels

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(though in a few cases these are rudimentary or lost), but no large folds in the branchial sac. The tentacles are always simple; the gonads are on one side only, in the immediate vicinity of the digestive tract.

Family Ascidiidae (Nomen Conservandum).

The body is not divided into a thorax and abdomen. The digestive and reproductive organs lie beside the branchial sac on the left side of the body. The branchial aperture most frequently has eight or seven lobes, the atrial six. The tentacles are simple and filiform. The dorsal lamina is a continuous (often toothed) membrane, or is replaced by a series of languets. The branchial sac has internal longitudinal vessels (which often bear papillae), but no large folds. The reproductive organs are in or spread over the surface of the intestinal loop.

Genus Ascidia Linnaeus (Nomen Conservandum)
= Phallusia Savigny.

These are simple ascidians, often of considerable size, with characters given above for the family. Papillae are present on the internal longitudinal vessels. Dorsal lamina consists of a continuous (often more or less toothed) membrane.

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Text Fig. 10.—Ascidia aspersa. (A) and (B) natural size, test removed. (A) Left side of zooid. (B) Right side of zooid. (C) Portion of branchial sac. × 40. (D) Diagram to show structure of dorsal tubercle, dorsal lamina, and neural gland.

Ascidia aspersa (Müll.). (Text Fig. 10; Plate 3, Fig. 10.)

For Synonymy and Literature see: 1930, Ascidia aspersa, Lindsay and Thompson, Journ. Mar. Biol. Ass., 17, pt. 1, p. 32.

This species is extremely common and is found singly or in clumps on the rocks between tide marks in all three localities. It is easily recognised by the elongate quadrilateral form of the body, and by the almost complete absence of colour (a small trace of pink or orange pigment in the siphonal linings being the only colour visible externally). The test is cartilaginous, is covered with fine papillae in young specimens, and is pustulose in older specimens. Attachment is, in most cases, by the posterior end and a small portion of the left side.

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Through pressure of the overlying individuals the posterior end of the test of specimens growing at the bottom of a clump may develop into a stalk-like process. Small specimens are usually without incrustations, but larger ones form a holdfast for small sponges, hydroids, polyzoa, compound ascidians, and seaweeds. The branchial aperture has eight lobes, the atrial aperture six. The lobes are short. In eighty per cent. of the specimens the distance between the two apertures is one third of the body length, and in the other twenty per cent. it ranges from one-quarter to one-half of the body length. Measurements based on the study of twenty-five specimens are: length, 1.7 to 7.5 cm.; breadth, 0.4 to 1.9 cm.; depth (measured below the atrial aperture), 1.3 to 2.0 cm.; distance between the apertures, 0.7 to 1.9 cm.; branchial siphon, 0.5 to 0.6 cm. long, 0.5 to 0 6 cm. wide; atrial siphon, 0.3 to 0.4 cm. long, 0.4 to 0.5 cm. wide; thickness of test, 0.2 to 0.3 mm.

The mantle is thin-walled and the musculature is not well developed. Muscle fibres are confined to the right side and the periphery of the left. In some specimens flecks of pink or orange pigment are present in the distal two-thirds of the right side of the mantle as well as in the siphonal linings. There are no longitudinal folds in the pharynx and the number of longitudinal vessels is between fifty-four and seventy-four, being always greater than the number of branchial tentacles. (The relationship between the number of longitudinal vessels and tentacles was found by Lindsay and Thompson, 1930 to be a means of specific differentiation in this genus.) There are no free papillae on the longitudinal vessels, but small vascular processes (Text Fig. 10C) are present. Branchial tentacles are simple, eighteen to thirty-four in number, and irregular in size and arrangement. The opening of the dorsal tubercle is basically a transverse oval, broader than it is high, with both horns inturned (Text Fig. 10B), but variations on this plan occurred in twenty-eight per cent. of the specimens. The neural gland is short and narrow and lies close to the nerve cord. The dorsal lamina is a continuous membrane with numerous transverse ridges on both of its sides and with a smooth edge. Five to seven narrow elongate stigmata are present in each mesh, but in a few specimens where the pharynx is abnormal and the longitudinal vessels are much reduced in size, the stigmata per mesh are few and short or in parts entirely lacking. The oesophagus is short, narrow, sharply-ridged on the outer border, and follows a semi-circular course. It leads to a short wide stomach bearing a few shallow longitudinal folds. The intestine is a wide, smooth-walled tube curving twice along its course and having the appearance of a capital N (Text Fig. 10A). The edge of the anal aperture is without lobes. Renal cells, colourless in young specimens but containing an orange or brown concretion in older specimens, follow the course of the gut and extend out over a portion of the mantle wall on the left side of the body.

The ovary and testis are both much-branched structures lying in the gut loop. The gonoducts run up parallel to the last loop of the intestine and open near the atrial aperture. Fertilisation is external and eggs and embryos were present in plankton hauls from the end of July, 1944, to the end of April, 1945. The eggs are surrounded by

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follicle cells which, under natural conditions, are lost even before the first cell division, but, under laboratory conditions, persist until the embryos are well developed. The tadpoles (Plate 3, Fig. 10) are white and the largest measured 3.7 mm. in length and 0.4 mm. in width in the head region.

Distribution: In New Zealand—Otago Harbour. Elsewhere—Europe from the Mediterranean to the Shetland Islands, with the exception of the East Coast of Britain north of the Thames (Lindsay and Thompson).

Remarks: It is difficult to account for the occurrence of this species in the Otago Harbour. It has not been recorded elsewhere in New Zealand, even from Stewart Island, which seems to have a similar ascidian fauna, and where fairly extensive collecting has taken place. There is, of course, the possibility that it has been brought on the hulls of ships, in which case it is surprising that it has not been recorded from the other main harbours. It seems more likely, as Professor Percival suggests, that when the Marine Biological Station personnel were endeavouring to acclimatize various English food fishes and crustaceans, ventures which were not at all successful, Ascidia aspersa was successfully introduced.

Family Rhodosomatidae hartmeyer.

This is a small but widely distributed and varied family of simple ascidians, characterised (in many cases at least) by the course of the intestine, which bends ventrally after leaving the stomach instead of dorsally as in most ascidians, thus coming to lie more or less on the right side of the body beside the branchial sac. Internal longitudinal vessels are commonly present, though sometimes rudimentary or lost; there are no large folds in the branchial sac.

Genus Corella Alder and Hancock.

In this genus the stigmata are arranged in small spirals. There is no valve or cover for the aperture.

Corella eumyota Traustedt. (Text Fig. 11; Plate 3, Fig. 11; Plate 5, Fig. 1.)

For Synonymy and Literature see: 1918, Corella eumyota, Michaelsen, Mitt. Mus. Hamburg, 35, p. 50.

This species (Plate 5, Fig. 1) is extremely common and is found singly or in clumps on rocks between tide marks in all three localities. The body is laterally compressed and pear-shaped with a terminal branchial aperture and an atrial aperture situated at the end of a short siphon which lies almost at right angles to the body and about halfway down it. This species is easily recognised by the posterior end of the intestine, which runs straight from the posterior end of the body towards the atrial aperture and can be seen through the colourless, transparent test. The siphonal linings and, in most cases, the mantle wall bear bright orange pigment. Attachment is, in most cases, by the right side, but the posterior end may be involved as well. The test is cartilaginous, smooth and usually free from incrustations, though small sponges, polyzoa, hydroids, etc., are sometimes present. The branchial aperture has eight lobes, the atrial aperture six. The lobes are short and not well-differentiated. Measurements based on the study of twenty-five specimens are: length, 1.4 to 4.2 cm.;

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breadth, 0.3 to 1.2 cm.; depth (measured below the atrial aperture), 0.5 to 2.5 cm.; distance between the apertures, 0.6 to 2.2 cm.; branchial siphon, 0.3 to 0.6 cm. long, 0.3 to 0.6 cm. wide; atrial siphon, 0.3 to 0.6 cm. long, 0.2 to 0.4 cm. wide; thickness of the test, 0.2 to 0.3 mm. (Note: Two exceptionally large specimens are recorded at the end of the description of the species.) The mantle is thin-walled and the musculature is not well developed. Muscle fibres are confined mainly to the left side of the zooid (Text Fig. 11A, B)

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Text Fig. 11.—Corella eumyota. (A) and (B) natural size, test removed. (A) Right side of zooid. (B) Left side of zooid. (C) Portion of bianchial sac. × 11. (D) Diagram to show structure of dorsal tubercle, dorsal lamina, and neural gland.

as also is any pigment present. There are no longitudinal folds in the pharynx wall and the number of longitudinal vessels is between seventy and ninety-two and is always slightly greater than the number of tentacles. There are no free papillae on the longitudinal vessels, but small vascular processes are present (Text Fig. 11C). Branchial tentacles are simple, fifty-six to seventy-eight in number, and belong to one or, less commonly, two orders of size. The opening of the dorsal tubercle in fifty per cent. of the specimens is of the type shown in Text Fig. 11D, and diverse variations were seen in the other fifty per cent. The neural gland is small and elongate and lies along the nerve cord. At the junction of the peripharyngeal grooves just behind the dorsal tubercle a long spoon-shaped process 1.0 to 2.0 mm. in length passes backwards (Text Fig. 11D). Behind this are situated the languets of the dorsal lamina which are twenty-two to thirty in number and coincide with every other transverse vessel. The stigmata are arranged in small spirals with no definite arrangement of right or left-handed ones (Text Fig. 11C). The gut loop is mainly confined to the posterior region of the right side of the body (Text Fig. 11B), but the terminal portion of the intestine passes around to the left side of the body and runs straight up towards the atrial aperture (Text Fig. 11A). The oesophagus is narrow and follows a short semi-circular course. The stomach is short and wide and, except for a small semi-circular region near the intestine, the wall is thrown into many folds which converge on to a median longitudinal groove. A well-developed typhlosole is present along the entire length of the intestinal wall. The edge of the anal aperture is without lobes.

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The ovary and testis are both much-branched structures and lie in the gut loop, being confined mainly to the right side (Text Fig. 11B). The gonoducts run parallel to the posterior loop of the intestine and open near the atrial aperture. Small white tadpoles (Plate 3, Fig. 11) were found in the mantle cavities of specimens collected between the middle of September, 1944, and the end of March, 1945. The largest measured 3.6 mm. in length and 0.4 mm. in width in the head region.

Distribution: In New Zealand—Kaipara Harbour, Hauraki Gulf, Queen Charlotte Sound, Lyttelton, Stewart Island (Michaelsen), Tauranga (Hartmeyer), d'Urville Island (Sluiter), Otago Harbour. Elsewhere—Chatham Islands (Sluiter), Chile, Valparaiso (Traustedt and Michaelsen), East Patagonia (Michaelsen), Brazil (Traustedt), South-West Coast of Africa (Sluiter and Michaelsen), Southern Indian Ocean (von Drasche), Tasmania (Kesteven), Auckland Islands (Herdman and Bovien), Antarctic-Graham Region (Sluiter and Arnbäck-Christie-Linde), Kaiser Wilhelm II Land (Hartmeyer), Falkland Islands (Arnbäck-Christie-Linde).

Note: Both Sluiter (1906) and Arnbäck-Christie-Linde (1938) record the presence of one giant specimen in their collections from the Antarctic. The author has found two giant forms on the Portobello Point—one 9.0 cm. long and 4.2 cm. wide, and another 10.3 cm. long and 5.8 cm. wide. In most respects these specimens are identical with C. eumyota, but tentacles are not only greater in number than would be expected (ninety being present in one and one hundred and fifty in the other specimen), but also show greater diversity in size, three or four orders being present as in C. borealis Traustedt. Arnbäck-Christie-Linde states that his large specimen had fifty tentacles, but gives no record of the orders of size. Both he and Sluiter concluded that giant forms occur within the species C. eumyota, and the occasional appearance of large specimens in a wealth of smaller ones certainly seems to indicate that some type of gigantism (? poly-ploidy) does occur.

Order Ptychobranchia Seeliger.

The most highly-specialised order of ascidians. It contains both compound and simple forms. The body is never divided into a thorax and abdomen; the digestive tract and reproductive organs always lie beside, or project only slightly behind, the branchial sac, which has internal longitudinal folds or plications (rudimentary or lost in a few forms). The tentacles are sometimes branched.

Family Botryllidae Verrill.

A small but widely distributed group of compound ascidians evidently belonging to the same stock as the Styelidae, and very closely related to some of the compound members of that family, in which Michaelsen, 1928, following the suggestion made by Arnbäck-Christie-Linde, 1923, has included them as a sub-family. They differ from the compound Styelidae in having the zooids arranged in well-developed systems with common cloacal canals discharging by common cloacal apertures instead of having the atrial apertures of the zooids opening separately and directly on the surfaces of the colony.

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Genus Botryllus Gaertner and Pallas.

Arnbäck-Christie-Linde and Michaelsen in their recent papers recognise two genera—Botryllus, forms with ovaries anterior or dorsal to the testis and no incubatory pouch, and Botrylloides (synonymous with Metrocarpa Arnbäck), forms with a single ovary with one large egg on each side of the body situated posterior to the testis and with an incubatory pouch present. In both genera the anterior margin of the atrial orifice may be produced into a long languet.

Botryllus leachi Savigny. (Text Fig. 12; Plate 2, Fig. 3; Plate 4; Fig. 4.)

For Synonymy and Literature see: 1922, Botryllus leachi, Michaelsen, Vidensk. Medd. naturh. Foren., bd. 73, p. 479.

This species forms soft, flat, irregularly-shaped masses on the sides and under-surfaces of rocks between tide marks in all three localities. Purple is the dominant pigment, but, as it varies in depth and as varying amounts of yellow or white pigment are present around the branchial apertures, a wide colour range occurs. The test is grey, semi-transparent, and the darker zooids and the terminal bulbs of vessels, especially numerous around the edge of the colony, show clearly through it. The zooids are arranged in extensive elongate or circular systems (Plate 2, Fig. 3) around the common cloacal apertures, which are inconspicuous and 1.5 to 3.0 mm. in diameter. Branchial apertures are 1.0 to 1.5 mm. in diameter and are without lobes. The largest colony measured 30 cm. in the longest diameter. The height above the substratum ranges from 2.0 to 5.0 mm., but does not vary greatly in the one colony.

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Text Fig. 12.—Botryllus leachi. Left side of zooid. × 30.

Zooids measure up to 4.5 mm. in length and 2.0 mm. in width The mantle is thin and bears a few widely separated muscle fibres It closely surrounds the zooid except on the dorsal side. The atria [ unclear: ] aperture is a large, straight-edged slit, distant from the anterior end of the zooid by about one-third of the body length. The pharynx is narrow, elongate, occupies almost the entire length of the zooid, and bears three longitudinal vessels on each side. The wall of the pharynx is broken by fifteen or sixteen rows of nineteen or twenty stigmata, arranged between longitudinal vessels as follows: endostyle 5/4/4/6–7 dorsal lamina. There are no marked differences in size of the transverse vessels. Branchial tentacles are sixteen in number and of three orders of size, regularly arranged. The dorsal lamina is a plain, straight membrane. The gut loop lies on the left side of the branchial sac, and is composed of a short, narrow oesophagus, which takes a semi-circular course; a wide-lobed stomach with nine folds arranged on a slight spiral and with a short, wide, upwardly-directed gastric caecum; and a wide, smooth-walled intestine covered for a certain

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portion of its length by an external intestinal gland. The edge of the anal aperture is without lobes.

Sex organs were not seen in any colonies collected before December, 1944. Small lobed testes were present in the zooids of a few colonies collected during that month, but ovaries could not be detected in any. In January and February, 1945, testes were present in the majority of the colonies examined. Ovaries were not discernible until the end of January, and then only in a few colonies. One or occasionally two eggs are present and they are situated level with or just in front of the much-lobed testis. The gonads on the left side lie higher up the pharynx than those on the right side. Small orange tadpoles (Plate 4, Fig. 4) were present in the cloacal cavities between the beginning of March, 1945, and the end of April, 1945. The largest measured 1.4 mm. in length and 0.27 mm. in width in the head region.

Distribution: In New Zealand—Hauraki Gulf, Tauranga, Stewart Island (Mich.), French Pass (Sluit.), Otago Harbour. Elsewhere—Auckland Island (Bovien), North-West Ireland, Northern France, Skaggerak and Kattegat (Mich.).

Remarks: As far as can be ascertained, the specimens described above are identical with those considered by Michaelsen to belong to the species Botryllus leachi.

Botryllus schlosseri (Pallas). (Text Fig. 13; Plate 2, Fig. 2; Plate 4, Fig. 5.)

For Synonymy and Literature see: 1922, Botryllus schlosseri, Michaelsen, Vidensk. Medd. naturh. Foren., bd. 73, p. 481.

This species is rare and has been found on the under-surfaces of rocks between tide marks at Goat Island and on the branches of Cystophora torulosa (R. Br.) at the Portobello Point. To date no specimens have been found at Quarantine Island. The colonies form firm, flat, irregularly-shaped masses. The test is in all cases light yellow and transparent. The zooids are purple, green, or brilliant orange in colour and are arranged in small circular or elliptical systems (Plate 2. Fig. 2) around the common cloacal apertures, which are almost circular, 1.0 to 2.0 mm. in diameter, and each of which serves as an exit for ten to twenty zooids. The systems may lie close together or be separated by distances of up to 1.0 cm. Traces of scarlet and white pigment are sometimes present

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Text Fig. 13.—Botryllus schlosseri. Left side of zooid. × 30.

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on the anterior ends of the zooids and on the edge of the common cloacal apertures. Branchial apertures are 0 8 to 1 0 mm. in diameter and without lobes. The largest colony measured 10 cm. in the longest diameter. The height of the colony above the substratum ranges from 1.0 to 4.0 mm., and does not vary greatly in the one colony.

Zooids measure up to 2.5 mm. in length and 2.0 mm. in width. The mantle is thin and bears a few widely separated muscle fibres. The mantle surrounds the zooid closely except on the dorsal side, and on this side it is produced above the atrial aperture into a long lappet-like process. The pharynx is wider than that of B. leachi and occupies almost the entire length of the zooid. There are three longitudinal vessels in the pharynx wall, which is broken by nine or ten rows of sixteen, nineteen or twenty stigmata arranged between the longitudinal vessels as follows: endostyle 5/3/3/5 dorsal lamina, or endo-style 5/4/4/6–7 dorsal lamina. There are no marked differences in size of the transverse vessels. Branchial tentacles are eight or sixteen in number and belong to two or three orders of size, regularly arranged. The dorsal lamina is a plain straight membrane. The gut loop lies on the left side of the branchial sac, and is composed of a short semi-circular oesophagus; a wide oval stomach with nine or ten folds arranged on a slight spiral and with a long tubular, much curved, gastric caecum; and a smooth-walled intestine, covered for a certain portion of its length by an external intestinal gland. The edge of the anal aperture is not lobed.

Sex organs were discernible only in the spring and summer months. A much-lobed testis and an ovary consisting of from one to three eggs are present on each side and are symmetrically arranged. The eggs form a slight arc anterior to the testis. The tadpoles (Plate 4, Fig. 5) are small, a light orange in colour, and were found in the cloacal cavities of specimens collected in March and April, 1945. The largest measured 0 8 mm. in length and 0.2 mm. in width in the head region.

Distribution: In New Zealand—North Island (exact locality not known) (Michaelsen), Otago Harbour. Elsewhere—East Coast of America and the whole of Europe (Michaelsen).

Remarks: As far as can be ascertained, the specimens described above are identical with those described by other systematists as B. schlosseri.

Family Styelidae Sluiter.

This is a large family found in all parts of the world and includes both simple and compound forms. Its members have both apertures square or four-lobed, simple filiform tentacles, a continuous dorsal lamina, and four (or less) curved longitudinal folds on each side of the branchial sac, which always has straight longitudinal stigmata. The compound forms do not have the zooids arranged in systems with common cloacal apertures.

Genus Asterocarpa n.gen.

Reproductive organs present on both sides of the body, arranged in clusters of few to many small hermaphrodite gonads fused partly or almost entirely by their adjoining ends. Gonoducts open at the

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free ends of the gonads irrespective of whether they are directed towards the atrial aperture or not. Testes lie between the ovary and the body wall. Ducts of the testes pass from both sides of the gonad to form the vas deferens. The atrial velum may be broad or narrow. Atrial tentacles in a single row at the base of the velum. Spinules imperfectly developed or absent.

Note: Since Huntsman's major work on this family (1913) the classification of the Styelidae has been based mainly on the structure of the gonad, the shape of the gonad, and the position of the gonoducts. Huntsman differentiated two genera with gonad structure as given for Asterocarpa—Cnemidocarpa with “gonads few to many, elongate placed in a single row on each side of the body, ducts opening near the atrial siphon”, and Pandocia with “gonads numerous, short and scattered (not in a single row), ducts opening towards the atrial aperture”. The new genus Asterocarpa is clearly separated from the above by the cluster arrangement of the gonads (Text Fig. 14) and by the fact that the gonoducts do not necessarily open towards or near the atrial aperture, but lying as they do at the periphery of the clusters may be very close to the branchial aperture and open towards it.

It may be necessary to include the whole “Cnemidocarpa humilis group” (Hartmeyer, 1927) in the genus Asterocarpa. This group is discussed later under the species Asterocarpa cerea, the type species of the genus.

Asterocarpa cerea (Sluiter). (Text Fig. 14; Plate 4, Fig. 1.)

For Synonymy and Literature see: 1922, Cnemidocarpa cerea, Michaelsen, Vidensk. Medd. naturh. Foren., bd. 73, p. 417.

The body is almost spherical in shape and specimens are found singly or in clumps on the sides and under-surfaces of rocks between tide marks in all three localities. This species is easily distinguished in the water by the maroon siphons with eight white internal longitudinal bands. The test in retracted forms is dirty brown, but in expanded forms is light brown with a tinge of pink. The test is smooth except on the outer edge of the siphons, where it bears numerous small warty processes. Attachment is either ventral or involves all or part of one side as well. In many of the larger specimens the body is almost entirely covered by small sponges, hydroids, polyzoa, red and green seaweeds, etc. Measurements based on the study of thirty-five specimens are: length, 1.3 to 3.5 cm.; breadth, 1.5 to 4.5 cm.; depth, 1.0 to 2.7 cm.; distance between the apertures, 0.8 to 1.5 cm.; branchial siphon, 0.5 to 0 7 cm. long, 0.4 to 0.6 cm. wide; atrial siphon, 0.6 to 0.8 cm. long, 0.3 to 0.4 cm. wide; thickness of test, 0.3 to 0.8 mm.

The mantle wall is thin and light yellow in colour. The musculature is well-developed around the siphonal regions and fine fibres radiate from them over the mantle wall but do not reach the mid-ventral surface. On each side of the pharynx wall there are four longitudinal folds, of which the first and fourth are slightly narrower than the others. Longitudinal vessels number forty-four to fifty-five on the right side, forty-three to fifty-seven on the left side, and the general arrangement is as shown:—

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Length of specimen. Arrangement of vessels on the right. Total.
1.8 cm. E.1(8)2(9)3(9)3(8)—D.L. 43
2.0 cm. E.2(10)2(10)3(10)3(9)—D.L. 49
2.9 cm. E.2(9)3(10)3(11)3(12)—D.L. 53
3.5 cm. E.2(8)3(9)3(12)3(12)—D.L. 52

Transverse vessels are irregularly arranged, there being seven to ten small vessels including one of intermediate size between two larger

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Text Fig. 14.—Asterocarpa cerea. Dissection showing body opened from the ventral surface, pharynx removed. × 2.

ones. Ten to fourteen narrow elongate stigmata are present in the meshes between the folds. Branchial tentacles are simple, filiform, twenty-seven to sixty in number, and usually of three orders of size, irregularly arranged. Two or four orders of size occur in occasional specimens. In seventy-five per cent. of the specimens the opening of the dorsal tubercle is an elongate oval with out-turned horns. The neural gland is a small cushion situated to the right of the nerve cord. The dorsal lamina is a smooth, untoothed membrane slightly narrower than the first pharyngeal fold. The gut loop occupies one-half of the width of the left side of the body and two-thirds of the length. The oesophagus is short and narrow. The stomach is elongate, slightly wider than the intestine, and the internal longitudinal folds show through by transparency. There is no pyloric caecum and the edge of the anal aperture is straight and unlobed. The atrial velum is narrow and bears one row of small atrial tentacles. These are swollen at the base (see Michaelsen, 1922, p. 421), and are of two types, simple filiform and knobbed sensory, but there is no definite arrangement of the types. The endocarps are large structures confined to the left side of the body. The maximum number is eighteen, the minimum twelve. They are arranged around and inside the gut loop, and in seventy-five per cent. of the specimens the arrangement inside the gut loop was one endocarp between the oesophagus and the rectum and four endocarps in a row in the wider portion of the gut loop as shown in Text Fig. 14.

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Gonads occur in clusters of which two to nine are present on the right side of the body, one or two on the left side, and the number on the right side always exceeds that on the left. Intermingling of the gonads of neighbouring clusters gives a superficial appearance of large, much-lobed gonads, and when such intermingling occurs in the mid-ventral line the gonads appear to form a continuous mass. The number of gonads per cluster is varied and ranges from one (present in one case only) to ten. The gonoducts are small and open at the periphery of the clusters. [As the gonoducts are not easily distinguished without the aid of a binocular, it can be understood why the earlier workers described this species as having gonads in the form of branched masses and recorded the presence of the larger gonoducts only. It is interesting to note that Hartmeyer (1927) speaks of the gonad mass of this species as composed of fused gonad tubes, and Michaelsen (1922) speaks of some gonoducts arising from the middle of the gonad mass, but does not depict them, though he does show the cluster arrangement of the gonads in the figure given (p. 420)]. The testis lies between the ovary and the body wall, and ducts from the testis pass from both sides of the gonad to form the vas deferens. Small pale pink tadpoles (Plate 4, Fig. 1) were found in the mantle cavity between the middle of September, 1944, and the end of April, 1945. The largest measured 1.25 mm. in length and 0 13 mm. in width in the head region.

Distribution: In New Zealand—d'Urville Island (Sluiter), Queen Charlotte Sound, Stewart Island (Michaelsen), Otago Harbour. Sluiter has also recorded this species from the Malayan Archipelago, but Michaelsen is very dubious about the veracity of this statement.

Remarks: From a careful survey of the descriptions of the type specimen of Cnemidocarpa cerea given by Sluiter (1900) and later by Hartmeyer (1927), and of the forms Michaelsen gives as synonymous, it is apparent that the Otago specimens belong to this species, and from a thorough study of the gonads it is obvious that this species cannot belong to the genus Cnemidocarpa, and must be placed in a new genus, which the author proposes to call Asterocarpa.

Note on the “Cnemidocarpa humilis group” Hartmeyer: Hartmeyer (1927) re-examined type specimens of C. humilis (Heller), C. cerea (Sluiter), C. gregaria (Kesteven), C. assymetra (Hartmeyer), and C. robinsoni Hartmeyer and placed them in a group that he named the C. humilis group on account of the characteristic form and relative position of the gonads. He also suggested the possibility of raising this group to a separate genus, but felt that at the time he did not have sufficient justification for such a step. From the author's observations it is apparent that C. cerea (Sluit.) must be placed in a new genus on account of the arrangement of the gonads and the position of the gonoducts, and from a study of C. gregaria, type specimen U562, kindly loaned by the Australian Museum [a species which is identical with C. cerea in all respects except a larger count of branchial tentacles (84, including some very small ones)], it is apparent that that species also is a true Asterocarpa and it is highly probable that the whole “C. humilis group” will be found to belong to the genus Asterocarpa.

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The specific descriptions of the majority of the “C. humilis group” have been based on the study of a few forms and the full range of variability is not known. Hartmeyer's summary of the group (1927, p. 175) reads as follows: “C. robinsoni ist ausgezeichnet durch mehr als eine, nämlich 2 oder 3 Gonaden auf der rechten Seite und besitzt gleichzeitig die geringste Zahl von Endocarpen; C. assymetra ist ausgezeichnet durch die nicht nur relativ (mit Bezug auf die Körpergrösse) sondern auch absolut geringste Zahl innerer Längs-gefässe und zusammen mit C. gregaria höchste Zahl von Endocarpen. Eine scharfe Abgrenzung der drei australisch-neuseeländischen Arten ist zur Zeit nicht möglich, und vermutlich dürfte ihre artliche Vereinigung sich später als notwendig herrausstellen. Als Unterschied zwichen C. gregaria und C. cerea wüsste ich nur die etwas geringere Zahl der Endocarpe bei letzterer anzuführen…. Die Diagnose von C. humilis ist lückenhaft.” In view of the above description of Asterocarpa cerea based on the study of thirty-five specimens, the grounds for the separation of C. robinsoni are no longer tenable, i.e., the presence of two or three fused gonad masses on the right side and the low count of endocarps. C. assymetra has a larger count of endocarps than any specimen of A. cerea examined and, although the count of longitudinal vessels of most specimens of C. assymetra fall within the range given above for A. cerea, in one specimen the extremely low total count of sixty-four was recorded. The differences between the type specimen U562 of C. gregaria and A. cerea are also very slight. It is apparent that the examination of a fair amount of material of A. cerea (one species of the C. humilis group) definitely strengthens Hartmeyer's suggestion that examination of further material may lead to the conclusion that all members of the group belong to a single circum-south-polar species.

Genus Cnemidocarpa Huntsman.

Gonads few to many, elongate, placed in a single row on each side of the body, ducts opening near the atrial siphon. Testes lie between the ovary and the body wall. Ducts of testes pass from both sides of the gonad to form the vas deferens. The atrial velum may be broad or narrow. Atrial tentacles in a single row at the base of the velum. Spinules imperfectly developed or absent.

Cnemidocarpa bicornuta (Sluiter). (Text Fig. 15; Plate 4, Fig. 8.)

For Synonymy and Literature see: 1922, Cnemidocarpa bicornuata, Michaelsen, Vidensk. Medd. naturh. Foren., bd. 73, p. 440.

Specimens are found singly in cracks in rocks or wedged in between oysters between tide marks in all three localities, but are rather rare except at Goat Island. The body is orange in colour, elongate parallel to a line joining the two siphons, and laterally compressed. The siphonal openings are situated at the summit of cone-like elevations of the body (Plate 4, Fig. 8), and of these the one carrying the branchial aperture is the longer. The siphonal linings bear four bands of magenta pigment, and small magenta crosses are seen at the summits of the cones in retracted specimens. The test is leathery, longitudinally ridged, and almost free from incrustations.

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Attachment is ventral or involves part of the sides as well. Measurements based on the study of twenty-five specimens are: length, 2.8 to 4.5 cm.; breadth, 1.0 to 2.7 cm.; depth at the branchial siphon, 2.2 to 4.3 cm.; depth at the atrial siphon, 1.2 to 3.0 cm.; branchial siphon, 0.7 to 1.1 cm. long, 0.2 to 0.4 cm. wide; atrial siphon, 0.6 to 0.7 cm. long, 0.2 to 0.3 cm. wide; distance between the apertures, 1.8 to 3 4 cm.; thickness of test, 1.0 to 1.5 mm. except at the base, where it may reach a thickness of 3.0 mm.

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Text Fig. 15.—Cnemidocarpa bicornuata. Dissection showing body opened from the ventral surface, pharynx removed. × 1.

The mantle wall is cream and the musculature is strongly developed. On each side of the pharynx there are four longitudinal folds, of which the first is usually the smallest and the fourth is usually the largest. Longitudinal vessels number seventy-three to one hundred and six on the right side and seventy-five to ninety-six on the left side, and the general arrangement is as shown:

Length of specimen. Arrangement of vessels on the right. Total.
2.9 cm. B.6(11)5(15)5(14)4(14)—D.L. 74
3.0 cm. E.5(10)4(14)4(19)4(13)—D.L. 73
3.3 cm. E.5(14)6(17)6(21)5(21)—D.L. 95
4 4 cm. E.6(9)3(22)4(23)5(22)1—D.L. 95

Transverse vessels are irregularly arranged, and there are four to six small ones between two large ones. Seven to ten narrow elongate stigmata are present in the meshes between the folds. Fine para-stigmatic vessels are invariably present. Branchial tentacles are simple filiform, fifty-four to one hundred and eight in number and of three, four or five orders of size irregularly arranged. The shape of the opening of the dorsal tubercle differs greatly in the different specimens, but the basic plan seems to be a simple horseshoe with inrolled horns. The neural gland is a narrow elongate structure lying along the nerve cord. The dorsal lamina is a plain wide membrane two-thirds of the width of the first pharyngeal fold. The gut loop is narrow and occupies the posterior half of the left side of the body. The oesophagus is short, narrow, semi-circular, and leads to a long, thin-walled stomach, the internal longitudinal folds of which show through by transparency. There is no pyloric caecum and the edge of the anal aperture is of three shapes—straight-edged and smooth, lobed, or hooded. The atrial velum is narrow and bears one row of fine atrial tentacles, which are not swollen at the base. Different types of atrial tentacle occur in different specimens. Some have only the fili-

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form type, others both filiform and knobbed, and still others filiform, knobbed and forked, and in those specimens with two or more types there is no definite arrangement of the tentacles. (Note: Atrial tentacles in this species show much more variation than is recorded by Michaelsen.) Small endocarps are scattered over the mantle wall on both sides of the body, there being seven to twenty-two on the right side, and seven to twenty-three on the left, of which two to five lie in the gut loop.

Two long gonads are usually present on each side, but two abnormal cases were noted, one with an extra gonad on the right side, and the other with a gonad missing on the left. The gonads are situated well up the mantle wall. The gonoducts are large and open near the atrial aperture. The testes lie between the ovary and the body wall, and the testis ducts pass from both sides of the gonad to form the vas deferens. From the condition of the gonads it is apparent that genital products ripen in the summer months, but tadpoles were not seen.

Distribution: In New Zealand—French Pass (Sluit.), Firth of Thames (Quoy and Gaimard), ? Queen Charlotte Sound, Stewart Island (Mich.), Otago Harbour. Elsewhere—? Chatham Island (Sluit.).

Remarks: Michaelsen includes in the species C. bicornuata those forms belonging to Sluiter's C. argillacea, which have violet pigmentation or are without any. There may be a wide colour range in this species, but the Otago specimens are all orange in colour, and in colouration as well as internal structure agree with Sluiter's description of the type (1900, pp. 2223).

Family Pyuridae Hartmeyer.

These are simple ascidians having the branchial sac with longitudinal folds (usually five to eight or more on each side) and generally with branching tentacles and straight stigmata. Dorsal lamina variable, usually replaced by a row of languets. A “liver” consisting of masses of tubules opening into the stomach is present, but there is no kidney.

Genus Pyura Molina.

This is the largest genus of the family, having elongate, longitudinally placed gonads, usually one (less often two) on each side of the body. Dorsal lamina replaced by a row of languets. The stomach is elongate. The external body surface is rough, but usually not spiny.

Pyura subuculata (Sluiter). (Text Fig. 16; Plate 4, Figs. 2, 12a.)

For Synonymy and Literature see: 1922, Pyura subuculata, Michaelsen, Vidensk. Medd. naturh. Foren., bd. 73, p. 406.

This species is common in all three localities, occurring singly or in clumps under rocks just below high water level, and forming large masses on the roofs of caves filled at high tide. The body is small and slightly longer than it is deep. The test is dull purple in colour, finely wrinkled, and usually free from incrustations. The expanded siphons are narrow elongate structures which either diverge as soon as they leave the body proper or run parallel to one another. The siphonal lining is a clear purple. Attachment is ventral or involves portions of

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the sides as well. Due to pressure from above, the ventral portions of the test of the lower specimens of clumps may become extended and a stolon-like arrangement results. Measurements based on the study of twenty-five specimens are: length, 1.3 to 2.6 cm.; breadth, 0.8 to 1.5 cm.; depth, 0.8 to 2.0 cm.; distance apart of the apertures, 0.5 to 0.8 cm.; branchial siphon, 0.4 to 0.9 cm. long, 0.2 to 0.3 cm. wide; atrial siphon, 0.3 to 0.8 cm. long, 0.2 to 0.3 cm. wide; thickness of test, 0.5 to 1.1 mm., except at the base, where it may reach a thickness of 3.0 mm.

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Text Fig. 16.—Pyura subuculata. Dissection showing body opened from the ventral surface, pharynx removed. × 2.

The mantle wall is bright purple dorsally, orange ventrally, and the musculature is strongly developed. Siphonal spinules (Plate 4, Fig. 12a) measure 0.033 to 0.055 mm. in length and 0.009 to 0.015 mm. in width. On either side of the pharynx there are seven longitudinal folds, the seventh, fifth and fourth being the largest, and the third, second and first decreasing in size in that order. Longitudinal vessels number seventy-three to one hundred and two on the right side and seventy-five to ninety-six on the left side, and the general arrangement is as shown:—

Length of specimen. Arrangement of vessels on the right. Total.
1.6 cm. E.(3)2(6)3(6)3(12)3(9)3(7)2(11)3—D.L. 73
1.7 cm. E.2(4)3(7)3(8)3(13)3(11)3(7)3(13)2—D.L. 85
2.0 cm. E.(5)3(9)4(13)3(15)4(14)4(10)3(12)3—D.L. 102

There is no regular arrangement of the transverse vessels. In the meshes between the longitudinal folds three to six stigmata are present, each being crossed by a fine parastigmatic vessel. The branchial tentacles are branched, twenty-two to thirty-two in number and are of three orders of size. Very short primary branches are present and occasionally even shorter secondary ones are found. In sixty per cent. of the specimens the opening of the dorsal tubercle is horseshoe-shaped with inrolled horns and with the opening of the horseshoe pointing to the right. Numerous variations occur in the

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remaining forty per cent. The neural gland is a narrow elongate structure lying close to the nerve cord. The dorsal lamina is composed of thirty-three to thirty-eight short curved languets, and there is no correlation between the number of languets and the size of the body. The gut loop is extremely wide and occupies the posterior half of the left side of the body. (In three specimens it was slightly longer, but never as much as two-thirds of body length.) Apart from a slight constriction near the anal aperture, very little difference in width is shown in the various parts of the gut. The anal aperture is not hooded or lobed. The “liver” is composed of five finely-divided lobes which open on the dorsal side of the stomach, the lobe nearest the intestine being the largest and being divided into two main branches. The atrial velum is straight and very narrow.

There is one long gonad on each side except in one specimen where that of the left side was missing. The gonoducts open near the atrial aperture. The gonad on the right side is divided into seven to eighteen lobes, that on the left into seven to fourteen. The lobes are hermaphrodite, pale pink in colour distally, scarlet proximally, and are arranged in a double row. Small pink tadpoles (Plate 4, Fig. 2) were found in the mantle cavity between the middle of September, 1944, and the middle of October, 1944. The largest measured 1.75 mm. in length and 0.22 mm. in width in the head region.

Distribution: In New Zealand—French Pass, Sumner (Sluiter), Lyttelton, Cape Brett, Stewart Island (Michaelsen), Otago Harbour.

Remarks: The Otago specimens are almost identical with the Lyttelton specimens in the Suter collection deposited in the Hamburg Museum and described by Michaelsen (1908) under the name P. subuculata (Sluiter) var. suteri. In 1922 Michaelsen decided that P. subuculata was a very variable species and that there was no object in separating the extreme ranges of variability as varieties. Hence var. suteri has been abandoned.

Michaelsen's description of Lyttelton specimens was based on the study of preserved material, but the size of his specimens falls within the lower range of size given for those from Otago. In internal structure two major points of similarity between the Otago and Lyttelton specimens are worthy of note. Both have small first and sixth folds, whereas the type was described by Sluiter as having seven wide folds, and both have a very small number of lobes per gonad. (Lyttelton specimens, “ca. 11”, Michaelsen, 1908; Otago specimens, seven to eighteen; P. subuculata, “ca. 24”, Michaelsen, 1922). It is of interest to note that Michaelsen doubted whether the Lyttelton specimens were fully grown, being about half the size of the type specimen, and suggested that, if this were the case, apparent differences between them could be explained as age differences. Specimens from Otago are all smaller than the type specimen and, as tadpoles are found in the mantle cavity of some of the lower size range, it would appear that at least some of them are fully grown. The author strongly suspects that, when a further survey has been made of the genus Pyura in New Zealand, var. suteri will be raised to specific rank.

Pyura cancellata n.sp. (Text Fig. 17; Plate 4, Figs. 6, 7, 12b.)

Four specimens were found under rocks near low water mark

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—two at the Portobello Point and two at Goat Island. (Fifteen specimens collected from Devonport and St. Heliers Bay, Auckland Harbour, are included in this report to give sufficient material on which to base the establishment of a new species.) The body is usually laterally compressed and somewhat rectangular in shape and the most characteristic feature is the short rampart-like extension of test surrounding each aperture (Plate 4, Fig. 6). The outer surface of the body is yellow-brown and leathery in appearance, and the expanded siphons are long narrow tubes with bright scarlet linings which are broken by four bands of white tinged with metallic green. Attachment varies according to the shape of the substratum, but is usually ventral or involves about two-thirds of one of the sides as well. The test often forms a holdfast for many incrusting organisms, but the region around the siphons is always clear. The test is cancellous in structure and can be separated into two layers, an outer leathery pigmented layer, and an inner more elastic non-pigmented layer connected to it by small rough papillae (Plate 4, Fig. 7). Measurements based on the study of nineteen specimens are: length, 2.4 to 3.7 cm.; breadth, 1.1 to 2.3 cm.; depth, 1.8 to 3.6 cm.; distance apart of the siphons, 1.7 to 2.5 cm.; branchial siphon, 0.7 to 1.0 cm. long, 0.4 to 0.5 cm. wide; atrial siphon, 0.5 to 0.7 cm. long, 0.3 to 0.4 cm. wide; thickness of test, 1.8 to 4.6 mm., of which the cancellous portion occupies up to 1.8 mm.

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Text Fig. 17—Pyura cancellata. Dissection showing body opened from the ventral surface, pharynx removed. × 1.5.

The mantle is scarlet in colour dorsally, orange ventrally, and the musculature is very strongly developed. Siphonal spinules (Plate 4, Fig. 12b) measure 0.020 to 0.026 mm. in length and 0.012 to 0.015 mm. in width. The number of longitudinal folds on each side of the pharynx is usually seven, but six or eight are present in a few specimens. There is no correlation between body size and number of longitudinal folds. Longitudinal vessels number ninety-eight to one

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hundred and fifty-three on the right side, ninety-seven to one hundred and forty-six on the left side, and the arrangement is as shown:

Length of specimen. Arrangement of vessels on the right. Total.
2.4 cm. E.(3)2(13)2(14)2(15)2(16)2(12)2(12)1—D.L. 98
2.5 cm. E.1(5)3(12)3(16)2(17)2(17)2(15)2(12)1—D.L. 110
3.6 cm. E.3(5)4(12)3(17)3(20)3(22)2(17)2(15)1—D.L. 129
2.8 cm. E.(13)3(13)3(12)3(16)3(17)3(17)4(16)3(13)—D.L. 139

Transverse vessels are irregularly arranged, but there are usually six or seven small ones between two large ones. In the meshes between the longitudinal folds five to seven narrow elongate stigmata are present, each being crossed by a fine parastigmatie vessel. The branchial tentacles are branched, sixteen to twenty-six in number, and of two orders of size. Long primary and short secondary branches are present. The shape of the opening of the dorsal tubercle is extremely varied and is the same in two specimens only. The neural gland is a narrow structure running parallel to the anterior half of the nerve cord. The dorsal lamina is composed of thirty-six to fifty-three short curved languets, and there is no correlation between the number of languets and the length of the body. The gut loop occupies almost the entire length and width of the left side of the body and is composed of a short narrow oesophagus, and a long stomach and intestine between which there is little difference in width. The anal aperture is faintly lobed. The “liver” is composed of either five lobes or five pairs of lobes and in either case the largest lobe or pair of lobes is nearest the intestine. The atrial velum is a narrow straight-edged membrane.

On each side of the body there is one long gonad divided into numerous orange hermaphrodite lobes. Twenty-six to fifty-one lobes are found in the right gonad and twenty-one to forty-five in the left gonad, and they are arranged in irregular double rows. The gonoducts open near the atrial aperture. Reproductive products had been expelled in the specimens collected in Auckland in January, 1945, but spawning probably occurs later in Otago. Tadpoles of this species were not seen.

Distribution: New Zealand—Otago Harbour, Auckland Harbour.

Remarks: As far as can be ascertained, this species is not identical with any previously recorded. Elevation of the test around the siphons also occurs in P. praeputialis Heller, but whereas in that species one rampart-like structure surrounds both apertures, in the species described above two rampart-like structures are present, one around each aperture. In the number of longitudinal vessels, branchial tentacles and gonad lobes and in the length of the gut loop the species described above is not unlike P. trita (Sluiter), but the cancellous nature of the test and the rampart-like elevations of test around each siphon should justify its position as a new species. The author proposes to call it P. cancellata.

Type Specimen: Otago Museum.

Note: Auckland specimens differed from the Otago ones in being smaller, in having seven pharyngeal folds in all cases, and in having a count of longitudinal vessels and of branchial tentacles that falls in the lower range given in the description of the species.

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Pyura pulla (Sluiter). (Text Fig. 18; Plate 4, Fig. 12c.)

For Synonymy and Literature see: 1922, Pyura pulla, Michaelsen, Vidensk. Medd. naturh. Foren., bd. 73, p. 385.

Specimens are found singly or in pairs among the weeds on the upper surfaces and sides of rocks near low water mark in all three localities, and resemble the algal growth so closely that they are easily overlooked unless the siphons are expanded. The bright red siphonal linings are very conspicuous. The body is large, round and dorso-ventrally flattened. Attachment is by the ventral surface and may involve a portion of one side as well. The test is a dirty brown and on the outer surface bears numerous short processes, irregular in shape and size. It is thick, cartilaginous, and fine sand grains are incorporated throughout. Measurements based on the study of fourteen specimens are: length, 3.4 to 7.5 cm.; breadth, 2.5 to 5.0 cm.; depth, 1.8 to 4.8 cm.; distance apart of apertures, 1.9 to 2.5 cm.; branchial siphon, 0.7 to 0.9 cm. long, 0.6 to 0.8 cm. wide; atrial aperture, 0.7 to 0.8 cm. long, 0.6 to 0.7 cm. wide; thickness of test, 0.8 to 2.3 mm., except at the base, where it may reach a thickness of 4 mm.

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Text Fig. 18.—Pyura pulla. Dissection showing body opened from the ventral surface, pharynx removed. × 1.

The mantle is brick red dorsally, orange ventrally, and the musculature is strongly developed. Irregular patches, light orange in colour, occur on the mantle wall and wine-coloured concretions are present in the cells adjoining the gut loop. Directly above the anterior end of the gut loop the mantle is produced into a slight swelling. Siphonal spinules (Plate 4, Fig. 12c) measure 0.07 to 0.09 mm. in length and 0.010 to 0.017 mm. in width. On each side of the pharynx there are five longitudinal folds, of which the fifth is the largest and the rest decrease in size towards the endostyle. Longitudinal vessels number one hundred and thirty-seven to one hundred and fifty-eight

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on the right side and one hundred and thirty-eight to one hundred and fifty-eight on the left side, and the general arrangement is as shown:—

Length of specimen. Arrangement of vessels on the right. Total.
3.4 cm. E.6(20)5(21)5(19)5(22)5(26)5—D.L. 139
5.1 cm. E.7(20)5(24)5(26)7(28)6(31)7—D.L. 176
5.5 cm. E.7(16)4(18)5(24)4(23)4(28)4—D.L. 137
5.5 cm. E.7(19)4(21)6(22)4(27)6(24)5—D.L. 145

There are no marked differences in the size of the transverse vessels. In the meshes between the longitudinal folds seven to nine stigmata are present, each being crossed by a fine parastigmatic vessel. Branchial tentacles are long branched structures, twenty-four to thirty-two in number and of three or four orders of size regularly arranged. Tertiary, and occasionally quaternary, branching is shown and, due to the length of the main branches, an extremely feathery appearance is achieved. The shape of the opening of the dorsal tubercle is as shown in the top figure of Plate 4, Fig. 9, and is like that of young forms of P. pachydermatina. The neural gland is a short structure lying parallel to the anterior one-third of the nerve cord. The dorsal lamina is composed of thirty-one to fifty-five short curved languets, and there is no correlation between the number of languets and the size of the body. The gut loop occupies the entire length of the left side of the body and one half of its width, and is composed of a short oesophagus and a long stomach and intestine, between which there is little difference in width. In the majority of specimens the wall of the intestine bears squarish structures such as occur in P. pachydermatina and in that species are given the name of “problematical organs”. The edge of the anal aperture is straight and smooth. The “liver” is composed of five pairs of orange feathery lobes, of which the largest pair is that next the intestine. The atrial velum is 2.0 to 3.0 mm. in width and slightly lobed.

The single gonad on each side is more or less divided into numerous hermaphrodite lobes arranged in a very irregular double row except at the posterior end of the left gonad, where little space is available and there is but one row of very small lobes. The gonad lobes are deep cream at the distal end and bright pink at the proximal end. Tadpoles of this species were not seen, but, judging by the condition of the gonads, tadpoles were liberated in the middle of January.

Distribution: In New Zealand—Sumner (Sluit.), New Plymouth, Wellington, Queen Charlotte Sound, Stewart Island (Mich.), Otago Harbour.

Remarks: The Otago specimens are in all respects in agreement with those described by Sluiter (1900), but in no case has the author seen the “liver” structure figured by Michaelsen (1922, p. 388). It is possible, of course, that the distinct division into two parts figured by him could be due to disease condition.

Pyura pachydermatina (Herdman). (Text Fig. 19; Plate 4, Fig. 12d.)

For Synonymy and Literature see: 1922, Pyura pachydermatina, Michaelsen, Vidensk. Medd. naturh. Foren., bd. 73, p. 389.

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This species, popularly known as the sea tulip or sea apple, is common in all three localities and is found near low water level on rocks and wharf piles. The body is large, ovate, somewhat laterally compressed and elongate parallel to a line joining the apertures. Attachment is by means of a long, transversely-wrinkled, leathery stalk, an outgrowth from the anterior end of the body. The test is thrown into six deep longitudinal grooves. Pink pigment is always present in the grooves, and in large specimens extends over the entire surface of the test. Young forms are distinguished by the whiteness of the test and the fact that a row of spinous processes, 1.5 to 2.5 mm. in length and 0.5 to 1.0 mm. in width, projects from the summit of each ridge. In older specimens these processes are represented by mounds 0.7 to 1.2 mm. in length and 3.0 to 4.0 mm. in width. The branchial and atrial siphons are short, and one side of each is formed by the body itself. The walls of the retracted siphons are thrown into five or six longitudinal folds. The body forms an anchorage for fine mossy seaweeds, and the stem is often completely masked by large green and red seaweeds, hydroids, sponges, and compound ascidians. The test is extremely leathery and white in colour except for the pink pigment present in surface areas. Measurements based on the study of twenty-five specimens are: length, 2.0 to 8.6 cm.; breadth, 0.9 to 3.6 cm.; depth, 1.3 to 5.5 cm.; stalk, 5.6 to 49.0 cm. long, 0.6 to 0.9 cm. wide at the proximal end, 0.3 to 0.5 cm. wide at the distal end; distance apart of the apertures, 0.5 to 3.5 cm.; branchial aperture, 1.0 to 1.5 cm. wide; atrial aperture, 0.9 to 1.2 cm. wide; thickness of test, 0.1 to 0.5 cm.

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Text Fig. 19.—Pyura pachydermatina. Dissection showing body opened from the ventral surface, pharynx removed. × 1.

The mantle is colourless and of tough consistency. Well-developed circular muscles surround the siphons, and single longitudinal muscles radiate out from the siphonal regions but do not reach the mid-ventral surface. Siphonal spinules (Plate 4, Fig. 12d) measure 0 053 to 0 061 mm. in length and 0.007 to 0.008 mm. in width. On either side of the pharynx there are six longitudinal folds, of which the first is slightly smaller than the rest. Longitudinal vessels number seventy-two to one hundred and sixty-one on the right and seventy-two to

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Fig. 1.—Lett: Two colonies of Distapha fasme [ unclear: ] ana. Right. Two colon [ unclear: ] es of Aplidium (Amaroucium) benhami. Both natural size. Fig. 2.—Portion of a colony of Botryllus schlosseri. Natural size. Fig. 3.—Portion of a colony of Botryllus leach [ unclear: ] Natural size Fig. 4.—Portion of a colony of Aplidium (Amaroucium) adams [ unclear: ] showing mound formation at the common cloacal aperture. The two small colonies almost encircled belong to the species 4 (A.) benham [ unclear: ] . Natural size

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Fig. 1.—Tadpole of Aplidium (Amaroucium) adamsi. × 35. Fig. 2.—Tadpole of Aplidium thomsoni. × 35. Fig. 3.—Tadpole of Aplidium (Amaroucium) benhami. × 35. Fig. 4.—Tadpole of Aplidium (Amaroucium) phortax. × 35. Fig. 5.—Tadpolc of Didemnum psammatodes var. maculatum. × 35. Fig. 6.—Tadpole of Diplosoma macdonaldi. × 35. Fig. 7.—Tadpole of Didemnum candidum. × 35. Fig. 8.—Tadpole of Polycitor (Eudistona) circumvallatum. × 35. Fig. 9.—Tadpole of Distaplia fasmeriana. × 35. Fig. 10.—Tadpole of Ascidia aspersa. × 36. Fig. 11.—Tadpole of Corella cumyota. × 35.

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Fig. 1.—Tadpole of Asterocarpa cerea. × 95. Fig. 2.—Tadpole of Pyura subuculata. × 95. Fig. 3.—Tadpole found in plankton nets between the beginning of November. 1944, and the end of February, 1945. (Unidentified.) × 95. Fig. 4.—Tadpole of Botryllus leachi. × 95. Fig. 5.—Tadpole of Botryllus schlosse [ unclear: ] . × 95. Fig. 6.—Pyura cancellata. Two-thirds natural size. Fig. 7.—Portion of test of Py [ unclear: ] a cancellata in transverse section. Fig. 8.—Cnemidocarpa bicornuata. Two-thirds natural size. Fig. 9.—Diagrams illustrating the shape of the opening of the dorsal tubercle of Pyura pachydermatina in specimens of different sizes, the most complex opening belonging to the largest specimen the least complex to the smallest specimen. Fig. 10.—Spicules of Didemnum candidum. × 210. Fig. 11.—Spicules of Didemnum psammatodes var. maculatum. × 210. Fig. 12.—Spinules of (a) Pyura subuculata; (b) Pyura cancellata; (c) Pyura pulla; (d) Pyura pachydermatina. × 460.

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Fig. 1—Under-sm [ unclear: ] e of a lock at the Portobello Point, Showing c [ unclear: ] mp lo [ unclear: ] mation in Co [ unclear: ] clla eum [ unclear: ] ota Also present are small white colonies of Didemau [ unclear: ] candidum and very small colomes of Ap [ unclear: ] dium (Am [ unclear: ] oncum) benham [ unclear: ] , discernible by the stellate arrangement of the zoo [ unclear: ] ds Natural size.
Fig. 2—Under-smtace o [ unclear: ] to [ unclear: ] k be [ unclear: ] ing colo [ unclear: ] es of Dis [ unclear: ] apha fasm [ unclear: ] na Natural size.

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one hundred and sixty on the left, and definite correlation exists between the body size and the number of vessels present. The general arrangement of the vessels is as shown:—

Length of specimen. Arrangement of vessels on the right. Total.
2.4 cm. E.3(8)1(10)1(12)1(12)1(11)1(11)—D.L. 72
3.0 cm. E.3(11)2(13)2(14)2(16)2(15)2(14)2—D.L. 98
7.0 cm. E.5(12)2(15)3(16)4(17)3(16)4(13)2—D.L. 112
8.6 cm. E.6(14)7(20)6(22)6(23)7(23)9(16)3—D.L. 162

There are three to six small transverse vessels between two large ones. In the meshes between the longitudinal folds seven to nine narrow, elongate stigmata are present, each being crossed by a fine parastig-matic vessel. The branchial tentacles are feathery, twelve to twenty in number, of three orders of size, and exhibit five orders of branching. The shape of the opening of the dorsal tubercle (Plate 4, Fig. 9) differs in different specimens and there is definite correlation between the complexity of the opening and the size of the specimen, simple openings being found in small specimens, and complex ones in large specimens. The neural gland is a small round cushion lying to the right of the dorsal tubercle either directly beneath it or slightly posterior to it. The dorsal lamina is composed of thirty-four to sixty-nine curved languets, and the number of languets is correlated with body size, more languets being present in the larger specimens. The gut loop occupies practically the entire length and more than half of the width of the left side of the body. The oesophagus is narrow. Little difference in width is shown between the stomach and intestine. “Problematical organs” (Watt, 1891) are present on the right side of the intestine either along the entire length or on the second half of the loop only. The anal aperture is wide, smooth-edged and extended dorsally to form a hood. The “liver” is composed of five or six pairs of feathery lobes, of which the largest are those nearest the intestine. The atrial velum is 2.3 to 2.8 mm. in width and is slightly lobed.

The single gonad on each side is divided into ten to twenty rectangular hermaphrodite lobes which are arranged along the gonoduct in a single row. The posterior end of the gonad on the left side is compressed in the gut loop and the lobes are reduced in size. The gonoducts open near the atrial aperture. One abnormality in gonad arrangement was seen—two gonads lying parallel to one another and opening separately were present on the right side of the body, and a single gonad was present on the left side. Well-developed eggs are olive green. Gonads were distended in specimens collected on 14th January, 1945, and completely evacuated in specimens collected on 28th January, 1945. Tadpoles of this species were not seen.

Distribution: In New Zealand—Cape Kidnappers, Sumner, Stewart Island (Michaelsen), Canterbury (Herdman), Otago Harbour (Watt). Elsewhere—Chatham Islands (Sluiter), South Australia, Tasmania (Herdman).

Remarks: As far as can be ascertained, the species described above is identical with P. pachydermatina (Herdman). P. pachydermatina f. spinosissima, recorded by Michaelsen, has not been seen in the Otago Harbour.

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Note: The most striking feature of P. pachydermatina is the fact that a great amount of change occurs as growth proceeds, and internal features such as the shape of the opening of the dorsal tubercle, the number of longitudinal vessels, and the number of languets of the dorsal lamina are correlated with the size of the body.

Field Key.

A list of the ascidians in the district under survey, together with a key for field identification, has been placed in “Fauna of the Otago Harbour” at the Portobello Marine Biological Station.

Observations on Ascidian Tadpoles.

Although Portobello Point bears an extremely rich and varied ascidian fauna, tadpoles of very few species appeared in plankton samples taken in the vicinity. Those of Ascidia aspersa alone were present in any quantity, and tadpoles of this species were taken from the end of July, 1944, until the end of April, 1945. Embryonic stages and tadpoles of this species showed maximum abundance in the summer months. The only other records of tadpoles in the plankton are: one specimen of Didemnum psammatodes, one specimen of Aplidium (Amaroucium) adamsi, and three small black unidentified tadpoles (Plate 4, Fig. 3) which appeared between the beginning of November, 1944, and the end of February, 1945. The fact that tadpoles of the other species were not netted probably indicates that either they are weak swimmers or, having a very short free-swimming life, they settle near the parents. The clumping of individuals of the one species (Plate 5, Fig. 1) so often seen in the district under survey would seem to support the latter idea. Well-developed tadpoles were found in the mantle cavities of twelve of the nineteen species and, in four cases, Distaplia fasmeriana, Didemnum psammatodes, Didemnum candidum, and Diplosoma macdonaldi, buds were present in unliberated tadpoles. Tadpoles of Distaplia fasmeriana are particularly large (Plate 3, Fig. 9), and in some cases attachment was effected within forty minutes of liberation.

The calendar below indicates the months of the year when tadpoles of the different species were present. Question marks have been inserted where the actual tadpoles were not seen, but the state of the gonads, ripe or evacuated, gave a clue to the time of release of the genital products. It is obvious from a perusal of the calendar that the majority of species produce tadpoles during the summer months and that tadpole production occurs over a longer period in those species belonging to families considered to be the more primitive in each of three main divisions of ascidians—the Krikobranchia, the Diktyobranchia, and (if the Botryllidae are ignored) the Ptycho-branchia. The species Asterocarpa cerea has a long production period, and hence the author considers the genus, of which it is the type, to be a lowly genus of the family Styelidae. The short period of tadpole production in highly specialised species is to be expected, as it would be possible for highly specialised tadpoles to exist only under optimum conditions, and they would have such efficent fixation mechanisms that a high percentage attachment would be ensured.

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Tadpoles figured in Plate 3 are all drawn to the same scale—X 35, but those on Plate 4 are drawn to a larger scale—X 95. It will be noticed that tadpoles belonging to members of the same family bear striking resemblance to one another in general body shape and the type of sucker developed, and also that a considerable range of size occurs in the tadpoles of members of the same family, e.g,. Polycitoridae, and in tadpoles of members of the same genus, e.g., Aplidium. The largest tadpoles seen belong to the order Krikobranchia, which is considered to be the lowest order of the ascidians. Of the highest order, the Ptychobranchia, the highest family represented in the district, the Pyuridae, have extremely small tadpoles, if one can judge by those of Pyura subuculata and by the size of the ripe eggs of the other species.

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Yearly Calendar of Tadpole Production—1944–45.
May June July Aug. Sep. Oct. Nov. Dec. Jan. Feb. Mar. Aprl.
Order Krikobranchia
  Aplidium thomsoni X X X X X X X X
  Aplidium (Amar.) phortax X X X X X
  Aplidium (Amar.) adamsi X X X X X
  Aplidium (Amar.) benhami X X X X
  Didemnum psammatodes X X
  Didemnum candidum X X
  Diplosoma macdonaldi X X X
  Polycitor (Eudis.) circum-vallatum X X X
  Distaplia fasmeriana X
Order Diktyobranchia
  Ascidia aspersa X X X X X X X X X X
  Corella eumyota X X X X X X X
Order Ptychobranchia
  Botryllus leachi X X
  Botryllus schlosseri X X
  Asterocarpa cerea X X X X X X X X
  Pyura subuculata X X
  Pyura pulla ?
  Pyura pachydermatina ?

Commensals.

The bivalve Modiolacra impacta (Herr.) is commonly found in the test of Asterocarpa cerea and is occasionally found in the test of Pyura pachydermatina, Pyura cancellata, and Cnemidocarpa bicornuata. Amphipods inhabit the common cloacal canals of the majority of compound forms, and copepods of the family Noto-delphidae are found in the branchial sac of Asterocarpa cerea, Cnemidocarpa bicornuata, Pyura subuculata, Pyura pulla, and Pyura cancellata. Another small crustacean, Polycheria antarctica, is sometimes found in the branchial sac of the simple forms and in the common cloacal cavities of the compound forms.

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Acknowledgments.

The author wishes to record her gratitude to the Committee of the Portobello Marine Biological Station for the use of all the facilities of the Station; to the Curator, Mr. W. Adams, who has always been most helpful; and to the Royal Society of New Zealand for a grant towards general equipment; to Sir William Benham for the gift of a complete set of Michaelsen's separates; to Miss E. J. Batham for the photographs included and for the collection and preservation of material at times when the author was absent from the Station; and to Professor B. J. Marples for general assistance.

Summary.

This paper gives an account of the nineteen species of ascidians found in the vicinity of the Portobello Marine Biological Station, Otago Harbour. A new genus, Asterocarpa, has been established to cover those forms of the family Styelidae with gonads arranged in clusters and with gonoducts at the periphery of the clusters. Cnemidocarpa cerea (Sluiter) and Cnemidocarpa gregaria (Kesteven) are found to be members of the new genus, Asterocarpa. The “Cnemidocarpa humilis group” Hartmeyer (1927) is discussed and support given to Hartmeyer's suggestion that the five species included in the group [C. humilis (Heller), C. cerea (Sluiter), C. gregaria (Kesteven), C. assymetra (Hartmeyer), C. robinsoni Hartmeyer] may be found to belong to a single circum-south-polar species. Four new species are described, Aplidium thomsoni, Aplidium (Amaroucium) adamsi, Aplidium (Amaroucium) benhami, and Pyura cancellata, and two other species, Ascidia aspersa and Diplosoma macdonaldi, are recorded from New Zealand for the first time. A yearly calendar of tadpole production is given, and the fact that tadpoles are produced over a longer period in the more lowly members of the various orders noted. Illustrations of tadpoles of thirteen of the species are given, and the similarity of those of members of the same family noted. The geographical range of the various species is recorded, but no attempt has been made to summarise geographical distribution, this being better left until a more comprehensive survey of the ascidian fauna of the whole of New Zealand is available.

References.

Arnback-Ghristie-Linde, 1938. Ascidiacea. Pt. 1. Further Zool. Res. Swed. Ant. Exp., vol. 3, no. 4, pp. 154.

Bovien, P., 1921. Ascidiae from the Auckland and Campbell Islands. Vidensk. Medd. naturh. Foren., bd. 73, pp. 3347.

Cottrell, A. J., 1912. On the Tunicata Styela coerulea: Trans. N.Z. Inst., vol. 45, pp. 168172.

Hartmeyer, R., 1901–11. Tunicata in Bronn's Klassenu-Ordnungen des Thier-Reichs. Leipzig.

—— 1911. Dies Ascidien der Deutschen Südpolar Expedition 1901–1903. Deutsch. Sudpol. Exp. Zool., bd. 4, pp. 403606.

—— 1912. Die Ascidien der Deutschen Tiefsee-Expedition 1898–1899. Deutsch. Tiefsee-Exp., bd. 16, pp. 225392.

—— 1927. Zur Kenntnis Plebobranchiater und Diktyobranchiater Ascidien. Mitt. Zool. Mus. Berlin. bd. 13. pp. 159196.

—— and Michaelsen, W., 1928. Ascidiae Diktyobranchiae und Ptycho-branchiae. Fauna S.W. Australia, vol. 5, pp. 253460.

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Hastings, A. B., 1931. Tunicata. Great Barrier Reef Reports, vol. 4, no. 3, pp. 69109.

Heller, C., 1878. Beitrage zur näheren Kenntnis der Tunicaten. Sitz. Akad. Wein., vol. 77, pp. 83110.

Herdman, W. A., 1882. Report on the Tunicata collected during the Voyage of the H.M.S. Challenger during the years 1873–1876. Pt. 1. Ascidae Simplices. Rep. Voy. Challenger. Zool., Vol. 6, pp. 1296.

—— 1886. Report on the Tunicata collected during the Voyage of H.M.S. Challenger during the years 1873–1876. Pt. 2. Ascidae Compositae. Rep. Voy. Challenger. Zool., vol. 14, pp. 1432.

—— 1891. A Revised Classification of the Tunicata. Journ. Linn. Soc. Lond. Zool., vol. 23, pp. 561–652.

—— 1899. Descriptive Catalogue of the Tunicates in the Australian Museum. Aust. Mus. Sydney, vol. 17, pp 1–135.

—— and Riddell, W., 1913. The Tunicata of the Thetis Expedition. Sc. Exp. “Thetis” Reps. Aust. Mus., Sydney, vol. 4, pp. 873–890.

Huntsman, A. G., 1913. The Classification of the Styelidae. Zool. Anz., vol. 41, pp. 482501.

Lindsay, S. T., and Thompson, H., 1930. The determination of Specific Characters for the Identification of Certain Ascidians. Journ. Mar. Biol. Ass., vol. 17, pp. 135.

Keśteven, H. L., 1909. Studies on Tunicata. I. Proc. Linn. Soc. N.S.W., vol. 34, pp. 276295.

MacDonald, J. D., 1859. On the Anatomical Characters of a Remarkable Form of Compound Tunicata. Trans. Linn. Soc. Lond., vol. 22, pp. 373375.

Michaelsen, W., 1908. Die Pyuriden des Naturhistorischen Museum zu Hamburg. Mitt. Mus. Hamburg, bd. 25, pp. 227286.

—— 1911. Die Tethyiden des Naturhistorischen Museum zu Hamburg. Mitt. Mus. Hamburg, bd. 28, pp. 109186.

—— 1919. Zu [ unclear: ] Kenntnis der Didemniden. Abh. Naturw. Hamburg, bd. 21, pp. 144.

—— 1921. Die Botrylliden und Didemniden der Nordsee und der zur Ostsee führenden Meeresgebeite. Wiss. Meersunters, vol. 14, pp. 99124.

—— 1922. Ascidiae Ptychobranchiae und Diktyobranchiae von Neuseeland und den Chatham-Inseln. Vidensk. Medd. naturh. Foren., bd. 73, pp. 359498.

—— 1923. Sudafrikanische Ascidien. Goteborgs Kung. Vet. Vit.-Samh. Hand., vol 26, pp. 123.

—— 1924. Ascidiae Krikobranchiae von Neuseeland, den Chatham und den Auckland Inseln. Vidensk. Medd. naturh. Foren., bd. 77, pp. 263434.

Nott, J. T., 1892. On the Composite Ascidians of the North Shore Reef. Trans. N.Z. Inst., vol. 24, pp. 305334.

Quoy, J. R. C. and Gaimard, J. P., 1834. Animaux Mollusques. Voy. de l'Astrolabe, Zool. 3, pp. 559–626.

Sluiter, C. Ph., 1900. Tunicaten aus dem Stillen Ocean. Zool. Jahrb. Syst., 13, pp. 135.

Studer, T., 1879. Die Fauna von Kerguelensland. Fr. Archiv. fur naturgeschichte., vol. 45, pp. 104141.

Traustedt, M. P. A., 1885. Ascidiae Simplices fra det Stillen Ocean. Vidensk. Medd. naturh. Foren. Kjobenhavn, ann. 1884, pp. 160.

Von Name, W. G., 1918. Ascidians from the Philippines and the Adjacent Waters. Bull. U.S. Nat. Mus., 100, vol. 1, pt. 2, pp. 49174.

—— 1921. Ascidians of the West Indian region and South-Eastern United States. Bull. Amer. Mus. Nat. Hist., N.Y., vol. 44, pp. 283494.

—— 1930. The Ascidians of Porto Rico and the Virgin Islands. N.Y. Acad. Sci., vol. 10, pt. 4, pp. 403534.

Watt, J., 1892. On the Structure of Boltenia pachydermatina. Trans. N.Z. Inst., vol. 24, pp. 334348.