CILIOPHORA, PROTOCILIATA 483 



shaped bodies, the nature of which is open to speculation. Some 

 authors think that they are nuclei — micronuclei (after Hickson) 

 or macronuclei (after Konsuloff). Metcalf considers that each 

 nucleus possesses both metabolic chromatin and reproductive 

 chromatin, the former being seen as large flattened peripheral 

 masses and the latter, as smaller spheroidal granules. 



In all except protociliates and a comparatively small number 

 of astomous euciliates, there is a cytostome which in its simplest 

 form is represented by a small opening on the pellicle, and may 

 or may not be closed when the animal is not feeding. The cyto- 

 stome opens into the cytopharynx (or gullet), a canal which ends 

 in the deeper portion of the endoplasm. In the cytopharynx there 

 may be present one or more undulating membranes to facilitate 

 intaking of the food. Occasionally the cytostome is surrovmded 

 by trichites or trichocysts (p. 62). When the cytostome is not at 

 the anterior region as, for instance, in Paramecium, there is a 

 peristome (or oral groove) which starts at or near the anterior end 

 and runs posteriorly. The peristome is ciliated so that food par- 

 ticles are thrown down along it and ultimately into the cytostome 

 which is located at its posterior end. Solid waste particles are ex- 

 truded from the cytopyge, or cell-anus, which is usually notice- 

 able only at the time of actual defecation (p. 92). 



Following Metcalf, Ciliata are here divided into 2 subclasses: 



2-many nuclei of one kind; sexual reproduction permanent fusion. . . 



Subclass 1 Protociliata 



Macronucleus and micronucleus; sexual reproduction conjugation. . . 



Subclass 2 Euciliata (p. 487) 



Subclass 1 Protociliata Metcalf 



The protociliates are exclusively inhabitants of the intestine 

 of Anura, excepting 3 species, 2 of which occur in Urodeles and 

 one in a marine fish. The body is covered uniformly by cilia of 

 equal length. There is no cytostome and the nutrition is parasitic 

 (saprozoic). The number of nuclei varies from 2 to several hun- 

 dreds, all of which are of one type. Asexual reproduction is by 

 binary fission. In a number of species sexual fusion of 2 gametes 

 has been observed (Fig. 225, a-d). Encystment is common. One 



^' Family Opalinidae Claus 



Genus Opalina Purkinje et Valentin. Highly flattened; multi- 

 nucleate; in amphibians. Numerous species. 



