158 



BIOLOGY OF THE PROTOZOA 



strength of these cytostomial supports seem to be entirely out of 

 proportion to such liy[)othetic'al needs of the organism. Thus in 

 all of the Chlaraydoflontidie the trichites form a tubular armature, 

 the ends making a circumoral ring which may project beyond the 

 ventral surface (Chilodon cucidlus). Such an aggregate, known as 

 an oral or pharyngeal basket, or pharyngeal armature, forms a more 

 or less definite cytopharynx. In some cases the trichites are 

 replaced by a compact corneus tube which extends deep into the 

 the endoplasm as in Nassnla aurea, Orthodon hamatus, Trachelius 

 ovum, etc. (Fig. 83). 



A 



B 



C 



Fig. 83. — A, Orlhodon hamatus with oral tube; B, Fronlonia leucas. with undulating 

 membrane on left margin of mouth; C, Trachelius ovum. {A and C, after Biitschli; B, 

 after Calkins.) 



In the Trichostomina the permanently open mouth always leads 

 into a more or less highly-developed gullet or cvtopharynx, while 

 peristomial cortical differentiations of various kinds lead to it. 

 The cytopharynx is usually provided with one or niore undulating 

 membranes, while membranelles, undulating membranes and cirri 

 may also be present in the peristome (Fig. 78, p. 150). 



The mouth region of the ciliates appears to be the focal point of 

 the longitudinal rows of cilia. In the generalized forms, such as 

 Aciinobolus radians, Prorodon teres, IloIojjJiri/a discolor, etc., the 

 mouth is exactly terminal and the rows of cilia run symmetrically 

 to the posterior end (Fig. 165, p. .378). In the majority of cases, 

 however, the mouth is not terminal but may be found at various 



