II 



PHYLUM PROTOZOA 



71 



In some cases the conjugating cells are of two sizes, union always 

 taking place between a large cell or megagamete and a small cell 



nu 



E 



FIG. 51. Heteromita rostrata. A, the positions assumed in the springing movements 

 of the anchored form ; B, longitudinal fission of anchored 'form ; C, transverse fission of 

 the same ; D, fission of free-swimming form ; E, conjugation of free-swimming with anchored 

 form ; E 3 , zygote ; E s , emission of spores from zygote ; F, development of spores ; fl.l, ante- 

 rior ; fl.2, ventral flagellum. (From Parker's Biology, after Dallinger.) 



or microgamete. In Volvox (Fig. 50) this dimorphism reaches its 

 extreme, producing a condition of things closely resembling what 



