EMBSTOLOGT 143 



ova in all the higher animals are produced by the 

 female and the spermatazoa by the male. 



Before fertilization the ovum discharges the polar 

 bodies, and it is claimed by some that the spermata- 

 zosLii also discharges similar bodies. 



In order to fertilize the ovum the spermatazoan 

 must find its way into the ovum, penetrating its cell- 

 substance, where it sets up the process of develop- 

 ment. Fertilization having taken place, next follows 

 the "enormously complex" process of karyokinesis. 



Thus I have ^stated in outline the differences be- 

 tween the methods of reproduction by the Protozoa 

 and the Metazoa. I will enumerate them : 



First. The Protozoa produce no eggs, while the 

 Metazoa produce eggs. 



Second. The Protozoa produce no spermatazoa, 

 but the Metazoa produce them. 



Third. The ovum of Metazoa discharges polar 

 bodies. 



Fourth. The spermatazoa probably discharge polar 

 bodies. 



Fifth. After fertilization, there takes place in the 

 nucleus of the ovum the "immensely complex" 

 process of karyokinesis, while the division of the 

 nucleus in the Protozoan is simple. 



Sixth. All Metazoa pass through the gastrula 

 stage of development, which stage is represented by a 

 double-walled cavity composed of two layers of cells. 



Seventh. A Protozoan is composed of only one 

 kind of cells, while a Metazoan is composed of more 

 than one kind, and generally of many kinds. 



It is evident that the evolutionist must bridge the 

 chasm between the Protozoa and the Metazoa. Little 

 has been done in this direction. 



Komanes says that there is " a suggestive foreshad- 

 owing of sexual propagatipn among the unicellular 



