PHENOMENA ACCOMPANYING FERTILIZATION 293 



two individuals come together as in pseudo-conjugation of gre- 

 garines; they secrete a common cyst membrane and then fuse 

 completely. 



In isogamic and often in anisogamic fertilization, fusion begins 

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



A 



B 



Fig. 146. — Cycloposthium bipalmatum and Diplodinium triloricatum; conjugation. 

 .1, 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; (', Diplodinium with migrating pronuclei in 

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

 nuclei. (After Dogiel.) 



(PolystomeUina, gregarines, etc., Fig. 123, p. 235). In Adinophrys 

 sol (Fig. 142) according to Belaf , one of the fusing individuals devel- 

 ops a pseudopodium which unites first with the other cell. 



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 



