52 



HANDBOOK OF PROTOZOOLOGY 



Copulation 



In the process of copulation two gametes take part. If the 

 two gametes are morphologically alike, they are called isoga- 

 metes; and if unlike, anisogametes. 



Isogamy, or hologamy, is typically represented by the 

 flagellate Copromonas subtilis (Fig. 24), in which there occurs, 



Fig. 24 Copulation in Copromonas subtilis. X1300. (After Dobell). 



according to Dobell, complete nuclear and cytoplasmic fusion 

 between two individuals. Each nucleus, after casting off a 

 portion of its nuclear material, fuses with the other nucleus. 

 The process is comparable to fertilization among the Metazoa. 

 The zygote thus formed encysts instead of carrying on an active 

 trophic life. Among the Sporozoa, isogamy is commonly found 

 in the gregarines such as Lankesterella (Fig. 123), Schizocystis 

 (Fig. 126), etc. It is also quite common in the Foraminifera 



Fig. 25 Macrogamete and microgamete of Volvox aureus. 

 XIOOO. (After Klein). 



(Figs. 73, 76). It perhaps occurs in the Radiolaria, although 

 positive evidence is yet to be presented (Fig. 102). 



Anisogamy seems to be more widely distributed. On the 

 whole the differences between the microgametes and macroga- 

 metes are comparable to those which exist between the sperma- 



