26 University of California Publications in Zoology [Vol. 20 



Cytostome 



The cytostome lies on the anterior ventral surface at the extreme 

 anterior end of the body. It is a large elongated asymmetrical pocket, 

 slender pyriform in outline but curved on its right side against the 

 nucleus. Its length is about 0.3 that of the body and its width 0.3 to 

 0.2 its own length. It leads into the cytoplasm near the center of the 

 body. Its large size, great flexibility and its slight projection ante- 

 riorly in a prominent lip all indicate its efficiency as a food-grasping 

 and enveloping organ. We have found it during the later stages of 

 binary fission, in the Plasmodium of multiple fission, but not in the 

 encysted condition. We have not been able to determine the exact 

 mode of origin of new cytosomes. Its location immediately adjacent 

 to the blepharoplast and nucleus necessitates a high degree of elas- 

 ticity, integrity and resistance on the part of these organelles and the 

 rhizoplasts arising from them. 



Neuromotor System 



The use of tlie term organ system to designate the complex, struc- 

 turally integrated apparatus which links together the nucleus and 

 motor organs and plays such a distinctive role at mitosis, seems jus- 

 tified by the canons of comparative morphology, unless it be that the 

 dogma of the Cell Theory blights such morphological license. This 

 organ system includes the blepharoplast (fig. A, 5, bl.) from which 

 spring directly the three anterior flagella {atit. fl.), the attached, pos- 

 teriorly directed undulating membrane {und. mem.) with its marginal 

 flagellum {m.fl.), and the deeper lying parabasal body {par. b.), and 

 a nuclear rhizoplast {n.rh.). The centrosome {ce7it.) lies within the 

 centroblepharoplast, emerging at mitosis with its own independent 

 centrosomal rhizoplasts {cent, rh.) joining the ends of the paradesmose 

 {parad.) to the parent blepharoplast. 



It is noteworthy from the standpoint of comparative cytology that 

 the motor organelles, flagella, and undulating membrane terminate 

 in and originate from the centroblepharoplast. The nucleus never 

 loses its connection, by one or more rhizoplasts, with this structure, 

 which also plays a dominant role in the drama of mitosis for at this 

 time there springs from it the centrosome, which later divides, forming 

 the paradesmose and its connecting rhizoplasts. To it also is attached 

 the enormously large parabasal body, a reservoir of chromatoidal sub- 



