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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
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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.