34 



INVERTEBRATE MORPHOLOGY. 



bristles upon which the animal creeps {Hypotrichous forms, 



Fig. 17, D). 



A definitely localized mouth-opening is always present, 

 situated frequently at the extremity of a peristomial groove 

 and leading into a gullet of variable extent, usually lined by 

 cilia, though sometimes furnished with a chitinous support 



Fig. 17. — A, Paramoscium ; B, Stentor; C, Vwiieella ; D, Euplotes. 



cv = coutiactile vacuole. n = nucleus. 



m = moutb. n' = micronucleus. 



my = myophaiie. tr = trichocyst. 



(Chilodon). There is, however, no special digestive tract, the 

 food-particles after traversing the gullet being received into 

 the body-protoplasm, where they are digested. Usually there 

 is a localized ogestive region, and in a few cases there is a 

 definite anal opening. The food is procured as in the Flag- 

 ellates by the currents set up in the water by the cilia carry- 



