Studies on the Freshwater Ciliates of New Zealand
An Annotated List of Species From the Neighbourhood of Wellington
Literature on the New Zealand fresh-water ciliates is available from late in the nineteenth century when Kirk (1885), Maskell (1886, 1887) and Schewiakoff (1892) published the results of investigations on this part of our fauna. No further studies apparently have been attempted. Kirk briefly described 13 species of Vorticella, 2 of which he regarded as new. Maskell published lists and descriptions covering 67 species, and 25 of these were regarded as new species, together with 5 new varieties and 1 new genus. Schewiakoff, although his paper is not available, is quoted in the Zoological Record, 1892, as having described 11 new species and 5 new genera from this country. These writers thus record 91 species, of which 38 are described for the first time. On examination, the descriptions of Kirk's and Maskell's species are inadequate to enable re-identification of those species described as new. The data, in most cases, are incomplete, vague and indefinite in many morphological points. So far as can be ascertained, only 1 of Maskell's species, Stentor striatus, has been recognised elsewhere, and is listed by Kudo (1946). Noland and Finley (1931) regard Kirk's descriptions of his 2 new Vorticella as insufficient to establish the species. Two of Schewiakoff's 5 new genera, Cranotheridium and Strobilidium are listed by Kudo, and 1 of his species is included.
No less than 37·3% of Maskell's species were described as new. It is strange, however, that none of these have been determined during the present investigation, particularly as many collections were made from the same streams from which Maskell collected. Also to be considered is the now well established fact that many species of ciliates are quite cosmopolitan in their distribution. Thus the number of species endemic to any one country will not be great. The facts suggest that Maskell was unable to recognise that much of his material comprised species previously described. Such may have been due to the difficulties under which he worked, or to insufficient use of the available literature; of the writers on ciliates up to 1887, he quotes but 2, Kent (1880–82) and occasionally Stokes (1888).
This paper is a summary of data accumulated during 2 years' investigation and includes notes and discussion on 28 species of freshwater ciliates found in New Zealand. It is recognised that as a list it is far from complete. Of the 28 species, 16 are new records from this country, the other 12 being listed by Kirk or Maskell. No specimens referable to Schewiakoff's species were determined. There is an obvious and very real gap in the knowledge of the ciliate fauna of New Zealand,
and this fact together with the more complete and accurate knowledge of the fresh-water ciltates that obtains in other countries makes it desirable that investigation of the Class be instituted.
Materials and Methods
Samples were collected from fresh-water streams, ponds and swamps at various localities about Wellington, and from other districts in New Zealand. The field samples were examined immediately after collection, and the known species, or ones readily identified, were listed. Species were cultured in the field samples, but where subcultures were desirable, hay infusions were made and used according to standard procedures. Schaudinn's and Bouin's fixatives were extensively used, especially for bulk fixation, Schaudinn's giving the better, results. Yocem's (1918) method for fixing and staining was rapid to use and gave good results. For observation of living specimens, the hanging drop method, or Comandon and de Fonbrune's (1938) oil chamber method proved invaluable. Both methods allow prolonged observation of specimens, and distortion is reduced to a minimum. Attempts were made to narcotise specimens using either the vapour, or dilute solutions, of isopropyl alcohol, Evipan-Sodium, Chloretone, magnesium sulphate, cocaine hydrochloride, ether, chloroform and others. Generally, specimens become grossly distorted when such substances are introduced into the culture medium, but used carefully, narcoties are valuable for slowing individuals to enable closer study of particular structures. A modification of Bills (1922) method, using isopropyl alcohol for narcotising Paramecium was very useful for this genus and also for Halteria grandinella. A drop of culture on a slide is exposed to the fumes of a 2% to 5% solution of iso-propyl alcohol in an alcohol chamber. This method was found to be more convenient and satisfactory than Bills' method of adding a solution of the alcohol to the culture.
List of Species and Discussion
Coleps hirtus Müller
This species, which Maskell first recorded in 1886, is a common one about Wellington, and is often found in infusions made by steeping hay in water. It is associated generally with Cyclidium glaucoma. C. hirtus has also been collected from Castle Point (a temporary rainwater pond), the Wainui-o-mata Reservoir, and from streams in and about Wellington City. The regular arrangement of the ectoplasmic plates, of which there are 15 or more rows; the 3, posteriorly placed, conical cirri and long, fine, caudal cilium; the large, sub-spherical macronucleus, and the pellicular denticles about the antero-terminal cytostome, features dealt with in particular by Noland (1925, 1937), Kahl (1930), and by other writers, are characteristic of the species, and are shown in the Wellington specimens. Kahl first drew attention to a variation in the number of rows of ectoplasmic plates, and Noland (1937) showed that such variation lies about a mean which is typical for each species. In C. hirtus the mean is approximately 20, but this number Avas not seen in the few specimens where rows were counted.
Of other species of Coleps where the number of rows has been determined, C. octospinus, a giant species, has about 24; C. amphacantha, a smaller and twisted form, has 24; C. incurvus has 16, and C. elongatus 13 rows.
Spathidium spathula Müller
A marsh-terrarium in which the native frog, Liopelma hamiltoni, was being kept contained large numbers of this ciliate. The frogs, together with wet moss, were brought to Wellington from the Coromandel Peninsula, Auckland, and it is possible that S. spathula was present in the moss. The species was seen on no other occasion, and has not previously been recorded from New Zealand. Though not studied in detail, it was readily recognised by its sac-like shape and obliquely truncated anterior extremity, its size (approximately 200μ long), by the trichites about the oral region (Woodruff and Spencer, 1922), the twining macronucleus and large posterior contractile vacuole.
Homalozoon vermiculare (Stokes)
This vermiform, flexible ciliate was collected from a stream in Beatrix Bay, Pelorus Sound, Marlborough. The species has not been recorded previously from New Zealand. A few specimens occurred in a culture of the field sample, in which they were associated with Paramecium bursaria. The characteristics of the local specimens of H. vermiculare agree with the account of Stokes’ (1888) Litonotus vermicularis, which has since been transferred to the genus Homalozoon. There are numerous contractile vacuoles in a row along one side, a moniliform macronucleus which extends almost the full length of the body, and a truncated anterior extremity which bears what are possibly trichites or trichocysts. Although not studied in detail, these features enabled the identity of the local specimens to be determined.
Lionotus fasciola (Ehrenberg)
This species has been recorded from an open-air aquarium on the roof of the Biology Block, Victoria University College. Maskell (1886) presumably refers to this species in his listing of Litonotus fasciola. Detailed investigation was not attempted, but the characteristic features of the species—the stout elongate neck, the absence of trichocysts, and the double macronucleus—were readily distinguished in the Wellington material.
Loxophyllum meleagris Dujardin. Plate 37, fig. 1
Two localities, the open-air acquarium above the Biology Block, V.U.C., and a small bush stream at Akatarawa, yielded samples containing this species, but in neither habitat were specimens numerous. There has been no previous record of the species from New Zealand. The local specimens agree in all characters of systematic value with the descriptions given by Kahl (1926) and Kudo (1946). They show (fig. 1) the laterally compressed form with small protuberances on the left surface (batteries of trichocysts which are contained in these, and in other protuberances along the dorsal surface, can readily be demonstrated with 70% alcohol containing Sudan III), the moniliform
macronucleus with micronuclei corresponding in number with the macronuclear segments, and the elongate collecting canal with a contractile vacuole in its course at the posterior one-quarter of the body length. One or more subsidiary vacuoles often develop along the course of a shorter collecting canal which extends posteriorly from the contractile vacuole. As these usually appear when specimens have been under prolonged observation, they may be correlated with the artificial conditions existing on the slide. A point of considerable interest was the paralysis and subsequent disintegration of a specimen of Stylonychia putrina which came into contact with the left side of L. meleagris. The paralysis followed almost instantaneously on contact, and was without doubt caused by the discharged trichocysts of Loxophyllum.
Chilodonella cucullulus (Müller)
This species was recorded by Maskell (1886) from Wellington, and was listed under its former generic name of Chilodon cucullulus. In the present investigation it occurred in large numbers in an excessive secretion of mucus on the bodies of dying Neochanna sp., a fresh-water fish taken at Masterton and kept in an aquarium. They were present also beneath a thin white scum which developed on the surface of the water in the aquarium, but were not detected on the bodies of healthy fish. It would appear from these observations that C. cucullulus may on occasion assume a saprozoic existence, in this case on the secreted mucus. The species has not been detected again since these observations were made.
Genus Paramecium Hill
Three species of Paramecium were observed: P. aurelia, P. bursaria and P. caudatum. Of the 3, P. caudatum is a new record for this country and was found in a sample from the Wainui-o-mata Reservoir. Both P. aurelia and P. bursaria appear to be more common than P. caudatum in this district; these 2 species occurred in several collections from about Wellington, and also from mid-Canterbury. They were recorded by Maskell. The systematic features of each of the species are similar in all respects to those described elsewhere (Wenrich, 1928; Ludwig, 1930). Lund (1941) has given an excellent account of the cytostome and cytopharynx of Paramecium. The description, which agrees in all respects with what is found in local Paramecia, contains details of the dorsal zone of long cilia and the ventral penniculus in the cytopharynx, the oesophageal fibres and food vacuole formation. A process of macronuclear disintegration, believed to be endomixis (Woodruff and Erdmann, 1914), regularly occurs in cultures of P. aurelia in our laboratories. The process is essentially similar to that described by Woodruff and Erdmann and consists of macronuclear fragmentation forming small, spherical or slightly sausage-shaped chromatin bodies which subsequently disintegrate, accompanied by division of the micronucleus and later reconstitution of the macronucleus. Transverse fission, an essential part of the process, precedes the re-formation of the macronucleus.
Genus Colpidium Stein. Plate 37, figs. 2 and 3
Colpidium colpoda and the smaller Colpidium striatum are frequently collected from pools and streams in and about Wellington, although neither species has been described previously from New Zealand. Both species readily sub-culture in hay infusions. Stokes' (1888) description for each species leaves no doubt that the Wellington specimens are identical with his specimens. In C. colpoda (figs. 2 and 3), which has been more fully studied in this instance, the structure of the cytostome (fig. 3), its membranes, and the cytopharynx are similar to what has been described in detail by Furgason (1940). It has been clearly demonstrated in this investigation that, at least in C. colpoda, the pre-oral suture (figs. 2a, 3) is formed by the longitudinal ciliary rows of the right side turning on to and running across the left side anteriorly to the cytostome. The most posterior of these now obliquely transverse rows terminates the longitudinal rows of the left side; thus the suture is in reality the line along which the 2 sets of ciliary rows meet. Anterior to the suture, the ciliary beat is obliquely across the body and parallel to the direction of the ciliary rows, while posterior to the suture the beat is directed posteriorly and is parallel to the longitudinal axis of the body. These characteristics have not been stressed, to my knowledge, by writers on the Colpidia.
Cyrtolophosis mucicola Stokes. Plate 38, fig. 6
The specimens for this, the first record of the genus Cyrtolophosis from New Zealand, were collected from a stream at Beatrix Bay in Pelorus Sound. The morphological characteristics and the habits of C. mucicola, described and figured by Stokes (1888) and again by Kahl (1926), are identical with the present material. The small size (about 26μ long, by 10μ wide); the banana-shaped body; the sparse, longitudinally disposed cilia; the structure, shape and ciliation of the ingestive apparatus; and the sup-spherical, sub-central macro-nucleus are features fully confirming this specific identification. Further, the structureless and almost invisible envelope of mucilage in which specimens usually are found is quite characteristic.
Urocentrum turbo Müller. Plate 37, figs. 4a and b, 5
This species, first recorded from New Zealand by Maskell (1886), was collected from 3 localities, the Hutt and Akatarawa Valleys and from Mount Johnstone, Wellington, during the present investigation. The short, squat body with its anterior and posterior ciliary zones (fig. 4a) separated by a deep, ciliated annulation; the tail; and the macronucleus which is bi-lobed and posteriorly placed, are features characteristic of the species. Some further information than is available in the literature has been obtained. There is some difference of opinion concerning the structure of the tail (fig. 4a and b), some writers (Kent, 1880–82) maintaining that it is a solid structure, others (Bhatia, 1936) that it is composed of fused cilia. In local specimens treated with 10% nigrosin solution, the tail breaks down to discrete cilia, the basal granules of which form a sub-triangular area on the posterior extremity. It is thus clear that the tail is composed of cilia in more or less close association. A small, rounded, shovel-shaped lappet (figs. 4a and b) is situated immediately dorsal to the tail and protrudes
beyond the posterior margin: I have not seen mention of this structure by previous writers, although in the Wellington material it is persistent and obvious. The inner portion of the cytopharynx (fig. 4b) does not taper evenly towards the cell mouth (the point of formation of the food vacuoles) as in other members of the family Frontoniidae. Instead, the walls of the innermost portion are widely and suddenly flared, so as to be almost recurved, the whole structure having the appearance of a short-stemmed, wide-based goblet. The forming food-vacuoles are at first transversely elongated to conform to this flared extremity, but slowly assume an elliptical shape and finally become spherical as they are liberated into the endoplasm of the anterior half of the organism. The cytostome is situated at the anterior extremity of a ventral, longitudinal depression (figs. 4a and b) which extends from the posterior extremity of the animal to the annulation encircling the mid-body region. The depression is assymetrical in cross-section (fig. 4b), being steeper and deeper on the left side, which is ciliated, than it is on the right, which is free of cilia. The cytostome opens on to the steeper left face of the depression and from it the cytopharynx extends, almost at right angles, towards the left.
Kidder and Diller (1934), in their account of macronuclear behaviour, have described the typical structure of the macronucleus of U. turbo. These investigators record finding “a small percentage” with 2 macronuclei. Of 105 specimens examined in the local material, 59 contained one macronucleus (fig. 4), 28, 2 (fig. 5b), and 28, 3 (fig. 5a) macronuclei. That these are functional macronuclei is suggested by their equivalence in size, and the great similarity between them in granulation and staining reaction (as with Ehrlich's acid haematoxylin). Individuals containing 2 or 3 macronuclei were found in much the same proportions in the three samples collected. The phenomenon would seem to be general in this district.
Cyclidium glaucoma Müller
Cyclidium glaucoma, reported first from this country by Maskell (1886), is an abundantly occurring species. Few samples are collected in which it is not present. It appears to thrive under diverse conditions. It has been collected from a depth of 52 feet in the Karori Reservoir, from unpolluted streams and from swamps and ponds; and is readily sub-cultured in hay infusions. The species from Wellington agrees in all essentials with the description given by Hoare (1927), although the macronucleus is not situated in the anterior third as he describes, but is more centrally placed. The small size (about 20μ long by half as wide); the sub-central, compact, spherical macronucleus and adjacent micronucleus; the hood-like membrane attached along the right edge of the peristome; the truncated anterior extremity which is devoid of cilia, and the long, posteriorly directed cilium are features of systematic value readily observable in local specimens.
Order Spirotricha Butschli
Bursaria truncatella Müller
This large species, which was collected once in the 2 years of this study and which has not previously been recorded from this country,
has been the subject of a previous paper (Bary, 1948) and need not therefore be treated further in this account.
Spirostomum ambiguum var. major Roux. Plate 38, fig. 7
Species of Spirostomum are well known to zoologists in this country and S. ambiguum has been recorded by Maskell from Wellington. The varietal form “major” has been identified during this investigation; local specimens agree in essentials with the descriptions given by Bishop (1923) and Kahl (1926). The variety was collected on 3 occasions, once from the Botanical Gardens, Christchurch, and twice from the Upper Hutt district, Wellington. The specimens are similar in most respects to those described by Bishop, Kahl and again by Kudo (1946). They are, however, slenderer animals and have a breadth: length ratio of 1·0: 12·5 to 15·0 instead of the 1·0: 10·0 which Kudo records, and they are also shorter, attaining a length of only 1200μ, whereas Kahl records specimens 2 millimetres long, and Kudo from 1 to 3 millimetres long. In spite of these differences, agreement with the varietal form is evident in all other features, such as, for example, the long moniliform macronucleus and relatively large vesicular micronuclei, the length of the peristome which extends posteriorly to the cytostome in the posterior half of the body, the pyriform contractile vacuole occupying up to one-eighth of the length of the body, and in the yellow-brown tinged, finely granular and strongly vacuolate endoplasm.
Stentor coeruleus Ehrenberg
The beautiful blue Stentor, S. coeruleus, of which this is the first record from this country, occurred plentifully in a single sample taken from a small, sluggish backwater at the Wainui-o-mata Reservoir. The species could not be maintained in culture, and though further samples were taken from the same source, it has not again been detected. Features which make this species outstanding are the deep blue colour, the widely flared anterior portion, the long moniliform macronucleus and conspicuous, longitudinal striations—the myonemes.
Halteria grandinella Müller. Plate 38, fig. 8
H. grandinella is another commonly occurring species, and has been collected, often in considerable numbers, from many localities. It was recorded by Maskell from 3 areas about Wellington. The 7 adoral membranellae described by Kudo (1946) were not detected. Other characteristics, however, are exactly similar to the descriptions given by Kudo and Kent (1880–82) for this species. Such include the size range (25–35μ long, 20–30μ wide), the urn-like shape (fig. 8), the setiform cirri arising in threes from obliquely placed equatorial grooves, the 15 frontals, the form of the peristome with its vibratile membrane and cirri, the rounded macronucleus and small micronucleus.
Genus Stylonychia Ehrenberg. Plate 38, figs. 9 and 10
The only previously recorded species of Stylonychia from this country is S. mytilus (listed by Maskell), which was encountered again during this investigation. Two more species are to be added—S. notophora Stokes (fig. 9) and S. putrina Stokes (fig. 10), both species
described in 1888. The species were collected from a stream at Beatrix Bay, Pelorus Sound, and again from the Wainui-o-mata Reservoir, and both species readily sub-culture in hay infusions. Specimens assigned to S. notophora (fig. 9) agree with the descriptions given by Stokes, with the exception that cilia are not present on the right of the peristome. Stokes states that both cilia and an undulating membrane are present along the right peristome border. Lund (1941) in his account of the oral structures of various ciliates, states that only a membrane is present in this position in the Stylonychia and this was borne out in the present material. Endoral fibrils, which arise on the right of the peristome towards its posterior tip, were not recorded by Stokes. It is possible that the cilia he mentions are in reality these fibrils whose lashing motion closely resembles fine cilia beating in co-ordination. The absence of cilia on the right of the peristome and the presence of endorsal fibrils occurs also in S. putrina (fig. 10) and is probably universal among the Stylonychia. The local S. putrina differed from the description given by Stokes in the extent the marginal and anal cirri extend beyond the body margins. The marginal cirri, according to Stokes, project posteriorly only, but in the Wellington material they projected for about two-thirds their length along the entire margin on the right, and for approximately half the length of the margin on the left. The 5 anal cirri usually all projected in the local specimens, but less often 4 of the 5 would be projecting. In Stokes' material 4 are described as projecting. There may be considerable variations in a single species of Stylonychia, even under controlled experimental conditions, as has been demonstrated by Giese and Alden (1938). With this fact in mind, it is reasonable, in spite of the discrepancies outlined, to assign the local material to S. putrina, especially as in all other characters there is such close similarity between these and Stokes' material.
Euplotes patella (Müller)
E. patella has previously been recorded by Maskell and was detected again during this investigation in a sample of water from Masterton. There were very few specimens, and apart from identification of the species, no studies were undertaken.
Genus Aspidisca Ehrenberg. Plate 38, figs. 11 to 13
Two species of Aspidisca, A. lynceus (fig. 13) and A. turrita (figs. 11 and 12) were collected during this investigation, both from fresh-water streams. Both species were present in a sample taken at Beatrix Bay, Pelorus Sound, and A. lynceus occurred in a second collection from the Wainui-o-mata Reservoir. This is the first record of A. lynceus from New Zealand, but A. turrita was reported from fresh-water at Wellington by Maskell (1886). Earlier writers (Kent. 1880–82) state that both these species inhabit sea-water, but in this instance, both were collected from fresh-water streams. Contamination of the stream in Pelorus Sound by salt-laden winds or spray could conceivably occur, but it would not account for the presence of A. lynceus at Wainui-o-mata, several miles from the sea, and from which only fresh-water species of ciliates have been obtained. Further, the samples from Pelorus contained other ciliates recorded only from
fresh-water such as Homalozoon vermiculare, Paramecium bursaria and Cyrtolophosis mucicola. Judging from these observations, and those of earlier writers (Kent, Maskell) it is evident that A. lynceus and A. turrita may occur in either fresh- or salt-water.
The 2 species are very similar in a number of respects, particularly their size ranges, which overlap, although A. lynceus (fig. 13) is slightly larger (35–40° long); their sub-triangular to ovoid shape, and the disposition of the 7 fronto-ventral and 5 anal cirri. However, from a laterial view, the pronounced spine on the dorsal surface of A. turrita (fig. 12) effectively separates the two species.
Order Peritricha Stein
Genus Vorticella Linnaeus. Plate 39, figs. 14–21
Four species of Vorticella have been identified of which 3, V. microstoma (figs. 16–18), V. nebulifera var. similis (figs. 14, 15), and V. brevistyla (figs. 19–21) are new records, and have been investigated more fully than the fourth, V. campanula, which was recorded by Kirk (1885). As aids for identifying vorticellids, Noland and Finley's (1931) method of using the length of the spasmoneme spiral, the presence or absence of thecoplasmic granules, and the size and rate of contraction of the contractile vacuole, proved valuable in this investigation.
V. microstoma Ehrenberg (fig. 16) has been redescribed by Noland and Finley. In each of the local specimens, the ovate body and narrower peristomal disc surrounded by a thin, ring-like margin; the long oesophageal fibres; the slender, contractile stalk (fig. 17); the absence of thecoplasmic granules, and the large size of the contractile vacuole are characteristics similar to those determined by Noland and Finley. Further, the habit of readily encysting (fig. 18) under artificial conditions, and the ability to live in highly polluted cultures are other features mentioned by these authors.
Vorticella nebulifera Müller and V. similis Stokes, previous to Noland and Finley, were regarded as separate species. As a result of their investigations, these authors are of the opinion that V. similis is not a separate species, but a varietal form of V. nebulifera. They expressed doubt as to the soundness of this opinion, V. nebulifera being reported as a marine. V. similis as a fresh-water species. Kent (1880–82), however, records that V. nebulifera may be found in fresh-water, and Kirk (1885) states that he found this to be so in Wellington. In the present instance, specimens collected from Upper Hutt possessed certain features which would link them to either form, but more particularly with the varietal form “similis.” The chief feature in which there is lack of agreement between local specimens and the descriptions of V. nebulifera occurs in the contracted state; the Wellington specimens are smooth and globular, while V. nebulifera is reported to be deeply puckered anteriorly. The local material and “similis” agree in all essentials except size range, the local specimens averaging approximately 10μ longer (Stokes' measurements range between 42 and 53μ long, the local specimens between 53 and 67μ long). There is, however, very close agreement with Noland and Finley's description of V. nebulifera var.
similis. The range of size of both body and peristomal disc (38 to 48μ wide) and the length of the spiral in the spasmoneme (57 to 60μ) [see fig. 15], the highly refractive thecoplasmic granules and the small contractile vacuole (5·5 to 7·0μ) and its rapid pulsation rate (once every 6 seconds) are characteristics of systematic value, all of which fall within their data. If Noland and Finley's action is accepted in the light of subsequent comparative investigation of these two possible forms, then the Wellington specimens are to be identified as V. nebulifera var. similis: if not, then the close similarity with V. similis warrants identification of the local specimens with this species.
Vorticella brevistyla D'Udekem (fig. 19) is identified from the description given by Kent, D'Udekem's paper not being available. This is regarded as a valid species by Kent and by Noland and Finley, though the latter authors do not give a description of it. The V. brevistyla described by Kent is similar to the Wellington specimens except that the latter have a longer stalk, and thecoplasmic granules are present. The body size (78 to 110μ long); elongate-pyriform shape; the length: breadth ratio of 2·0: 1·0, and the comparative size of the disc (32 to 39μ wide) are similar. When contracted (fig. 21), an anterior, teat-like protrusion is common to both, but in this state the Wellington specimens are slightly ovoid, not spherical as described by Kent. The stalk (fig. 20) length of local specimens is once or twice the body length, whereas V. brevistyla is reported to have a stalk but half the length of the body. Noland and Finley, however, point out that the stalk length varies considerably within a species, and this is readily verified, so that this difference between the local and Kent's material cannot be considered a constant one. Unfortunately, Kent does not record whether V. brevistyla has thecoplasmic granules; the local specimens possess these granules (fig. 20), which are colourless and in a more or less double row along the entire length of the stalk. This discrepancy does not necessarily debar identification of the organisms from Wellington as V. brevistyla, since earlier writers (Stokes, Kent) invariably omitted recording these granules in species of Vorticella. Reproduction is by longitudinal fission and occurs readily, even while on a slide. Of the two daughters, one remains attached to the original stalk and the other assumes the form of an elongated, cylindrical telotroch which eventually breaks free and swims away.
From this survey, and those made by Maskell and Kirk, it is obvious that the fresh-water ciliates of New Zealand are very similar to those described from other countries. And this in spite of the commonly accepted, long-standing geographical isolation of these islands. Ciliates have been investigated in Australia (Whitelegge, 1899; Playfair, 1914; Gillies, 1915; Shephard, Searle and Strickland, 1918), where it has been shown that new species are rare. Bhatia (1922) concluded that the ciliate fauna of India, even to highly specialised forms, was very similar to that of Europe. Edmondson (1910), after investigating the protozoa of U.S.A. and Tahiti, states that all the evidence indicates that many species of protozoa are widely distributed throughout the United States and that many of
these same species are common in oceanic islands. The same is true for the Subantarctic; Murray (1910) has illustrated a number of ciliates collected from pools at Cape Royds (77° 30′ South) during the summer. These, though difficult to identify because of lack of detail, show at least that the species present are not markedly different from those found elsewhere. Schewiakoff as early as 1893 had concluded that the European forms were in the main cosmopolitan; he had investigated ciliates in North America, the Sandwich Islands, New Zealand, Australia and the Malay Archipelago. It is thus not surprising to find the close correlation between the ciliate fauna in New Zealand and that of other countries, and it can reasonably be expected that further investigations of the Class will but strengthen this view.
I wish sincerely to thank Professor L. R. Richardson for his help during the study and the preparation of the manuscript, and also Mr J. Johannson, Chief Chemist of the Wellington City Council, who, by his ready assistance, made it possible to make regular trips to the City Reservoirs for the purposes of collecting.
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Explanation of Plates 37, 38, and 39
Fig. 1—Loxophyllum meleagris, a fully extended specimen, from the right side.
Fig. 2—Colpidium colpoda, live specimens. (a) From the right side; the course of the ciliary meridians is indicated. Note the antero-ventral swing in the course of the meridians. (b) From the left side, showing the frontal suture.
Fig. 3—Colpidium colpoda, fixed and stained specimen showing the ciliary meridians as seen from the ventral aspect. Note that the right-hand meridians swing on to the left side to form the pre-oral suture (PR.S.) where they meet the longitudinal meridians of the left side.
Fig. 4—Urocentrum turbo. (a) Live specimen from ventral aspect. (b) Posterior view of specimen.
Fig. 5—Urocentrum turbo, fixed and stained specimens. (a) Individual with three macronuclei. (b) Individual with two macronuclei.
Fig. 6—Cyrtolophosis mucicola, live specimen, within mucilaginous envelope.
Fig. 7—Spirostomum ambiguum var. major, live specimen from the right side.
Fig. 8—Halteria grandinella, live specimen from the ventral aspect.
Fig. 9—Stylonychia notophora, live specimen from the ventral aspect. One micronucleus is lying beside each macronuclear body.
Fig. 10—Stylonychia putrina, live specimen from the ventral aspect.
Fig. 11—Aspidisca turrita, live specimen from the ventral aspect.
Fig. 12—Aspidisca turrita, lateral view to show dorsal spine. Free-hand diagram.
Fig. 13—Aspidisca lynceus, live specimen from the ventral aspect.
Fig. 14—Vorticella nebulifera var. similis, fully extended live specimen from the left side. The number of the oesophageal fibres has not been determined accurately in this, or other vorticellids in this paper.
Fig. 15—Vorticella nebulifera var. similis, the stalk, showing the spasmoneme and theeoplasmic granules.
Fig. 16—Vorticella microstoma, fully extended live specimen from the left side.
Fig. 17—Vorticella microstoma, posterior extremity and stalk.
Fig. 18—Vorticella microstoma, an encysted specimen.
Fig. 19—Vorticella brevistyla, fully extended live specimen from ventral aspect.
Fig. 20—Vorticella brevistyla, the stalk, showing the spasmoneme and thecoplasmic granules.
Fig. 21—Vorticella brevistyla, fixed and stained individual. The teat-like protrusion on the anterior extremity of contracted forms is barely perceptible in this specimen.
Note.—All figures have been drawn with the aid of a camera lucida. Micronuclei are shown when their size or position permit.
Abbreviations.—C.C., collecting canal; C.M., outer cytostomal membrane; C.V., contractile vacuole; CY., cytostome; CYT., cytopharynx; F., endoral fibrils; F.V., food vacuole; L., posterior lappet; M, 1–3, cytopharyngeal membranes; MAC, 1–3, macronucleus (macronuclei); MIC., micronucleus; MY., myoneme; O.F., oesophageal fibres; PR.S., pre-oral suture; T., tail; V., vestibule; V.G., ventral groove; V.M., vibratile membrane.