334 Ciliophora 



tion, whereas nuclear dimorphism (macronucleus and micronucleus) is 

 characteristic of the Euciliatia. 



Subclass 1. Protociliatia 



These are the opalinid ciliates which, except for a few species from 

 fishes and snakes, are parasitic in the large intestine of Amphibia. The 

 opalinids have no cytostome, although this is not a feature exclusive to 

 them among the Ciliatea. The distribution of cilia is practically uniform 

 and in this respect the opalinids resemble many holotrichous ciliates with 

 which they have sometimes been classified. 



Ciliary patterns are rather simple. As described in Opalina obtrigo- 

 noidea (43), the dorsal rows follow sigmoid paths while the ventral rows 

 are relatively straight (Fig. 7. 1, A). About half of the rows pass com- 

 pletely around the body. The rest, intercalary rows which extend from the 

 anterior end toward one margin of the body, possibly represent stages in 

 the development of new rows (43). Similar intercalary rows have been 

 described in Zelleriella elliptica (38) and other species (152). Along the 

 anteroventral surface in O. obtrigonoidea, a number of stout falcular 

 cilia arise from the falcular fibrils (Fig. 7. 1, C, E). The latter are two 

 subpellicular fibrils which extend along the anteroventral margin and 

 then fuse into a single fibril which continues for some distance along the 

 left margin of the body. The falcate fibril is connected with the first basal 

 granule in each row of somatic cilia (Fig. 7. 1, E). Although longitudinal 

 fibrils joining basal granules could not be detected, oblique fibrils, per- 

 pendicular to the rows of cilia, connect basal granules of different longi- 

 tudinal rows (Fig. 7. 1, D). In addition to the fibrils parallel to the body 

 surface, dorso-ventral fibrils extend inward from the basal granules, usu- 

 ally passing to granules on the other side of the body (Fig. 1. 11, G). 

 In contrast to an earlier report for Opalina rananun (73), no connections 

 between the fibrils and the endoplasmic spherules could be detected in 

 O. obtrigonoidea. The absence of such connections also has been reported 

 for Cepedea metcalfi, Opalina coracoidea, and O. ranarian (8). 



The pellicle of opalinids (8, 43, 152) shows ninnerous grooves, parallel 

 to the rows of cilia, and each row apparently arises in such a groove. In 

 O. obtrigonoidea the grooves are produced by pellicular folds (Fig. 7. 1, 

 B) which may be a factor in maintenance of body form, "functioning 

 much like the corrugations in corrugated cardboard" (43). Myonemes 

 have not been demonstrated in the cortex. 



The endoplasm typically contains Feulgen-negative (177) endoplasmic 

 spherules (endospherules, endosarc bodies) which have been interpreted 

 variously as Golgi bodies, parabasal bodies comparable to those of certain 

 flagellates, masses of stored food, and even as stages in the development 

 of nuclei. There is no evidence that these endoplasmic spherules are 

 homologues of the macronuclear derivatives in Dileptiis (Chapter I). Al- 



