CILIOPHORA, PROTOCILIATA 685 



astomatous 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 cytostome opens into 

 the cytopharynx (or gullet), a tubule which ends in the deeper por- 

 tion 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 surrounded by trichites or trichocysts 

 (p. 71). 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 particles are thrown down along it and ulti- 

 mately into the cytostome which is located at its posterior end. Solid 

 waste particles are extruded from the cytopyge, or cell-anus, which 

 is usually noticeable only at the time of actual defecation (p. 108). 

 Cytology (Konsuloff, 1922; Wetzel, 1925). 



Following Metcalf, Ciliata are here divided into 2 subclasses: 



Two to many nuclei of one kind; sexual reproduction permanent fusion. . . 



Subclass 1 Protociliata 



Macronucleus and micronucleus; sexual reproduction conjugation 



Subclass 2 Euciliata (p. 690) 



Subclass 1 Protociliata Metcalf 



The protociliates are almost exclusively inhabitants of the large 

 intestine of Salientia; only a few species have been reported from 

 urodeles, reptiles, and fish (Metcalf, 1923, 1940). The body is cov- 

 ered uniformly by cilia of equal length. There is no cytostome and 

 the nutrition is parasitic (saprozoic). The number of nuclei varies 

 from two to many, all of which are of one type. Asexual reproduction 

 is by binary fission or plasmotomy. In a number of species sexual 

 fusion of 2 gametes has been observed (Metcalf, 1909; Konsuloff, 

 1922) (Fig. 294, f-i). Grasse (1952) proposed recently to transfer 

 these organisms to "Rhizoflagellata" from Ciliata, since they differ 

 from the ciliates in (1) having nuclei of the same kind, (2) under- 

 going sexual fusion and not conjugation, and (3) having longitudinal, 

 and not transverse, division or plasmotomy. Taxonomy (Metcalf, 

 1920a, 1923, 1940); geographical distribution (Metcalf, 1920, 1929, 

 1940); cytology and development (van Overbeek de Meyer, 1929); 

 species (Bhatia and Gulati, 1927; Carini, 1938-1942; Beltran, 1941, 

 1941a). 



Family Opalinidae Claus 



Genus Opalina Purkinje and Valentin. Highly flattened; multi- 

 nucleate; in amphibians. Numerous species (Metcalf, 1923, 1940). 



