20 



BIOLOGY OF THE PROTOZOA 



conceptions of a cell. In perhaps the majority of the Protozoa the 

 fundamental vital activities are performed, as in the simpler Ameba 

 or simple flagellates, by the protoplasm as a whole and without other 

 visible specializations than nucleus and cell body. In other forms, 



Mac. 



Mic.-- 



C.V.- 



Fig. 2. — Diplodinium ecaudatum, a parasitic ciliate in cattle. A, anal canal and 

 defecatory vacuole; C. V., one of the two contractile vacuoles; M, motorium with 

 fiber to circumpharyngeal ring; Mac., macro nucleus ; Mic, micronucleus ; S, skeletal 

 layer. (After Sharp.) 



however, intracellular differentiations lead to intracellular division 

 of labor which in some types becomes as complicated as are many 

 of the organisms belonging to the Metazoa. Thus Diplodinium 

 ecaudatum, one of the Infusoria, according to Sharp (1914), has 

 intracellular differentiations of extraordinary complexity (Fig. 2). 



