PHENOMENA ACCOMPANYING FERTILIZATION 



517 



as a rule with union of the flagellated ends, if the gametes are motile 

 as in Scytomonas, Polytoma, PolystomeUa and gregarines, etc. 

 (Fig. 96, p. 211). In Actinophrys sol (Fig. 209) according to 

 Belaf , one of the fusing individuals develops a pseudopodium which 

 unites first with the other cell. 



^ 



B 



Fig. 213. — Cycloposthium hipalmatinn and Diplodinium triloricatum; conjugation. 

 A, Cycloposthium with the two migrating pronuclei in the chamber formed by the 

 two peristomial spaces; B, same, the two migrating pronuclei have passed from the 

 peristomial chamber into the gullets; C, Diplodinium, with migrating pronuclei in 

 the peristomial chamber in their passage from one individual to the other; p, pro- 

 nuclei. (After Dogiel.) 



With anisogamic fertilization the microgamete is usually motile, 

 the macrogamete is stationary and is sought by the microgamete 

 and the same is true also of oogamic fertilization. In some cases 

 the macrogamete is smaller than the migrating microgamete 

 (Fig. 183, p. 427). In the VorticeUidae the macrogamete remains 

 attached while the microgamete is free-swimming. 



