FERTILIZATION 



61 



As has been suggested above, the eggs have much 

 attraction for the sperms vi^hen they come near to one 

 another. The sperms move toward the egg, attach 

 themselves to the surface, and one of them (usually only 

 one) succeeds in penetrating the egg membrane. The 

 sperm enters the protoplasm of the egg. When it is in 





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A ■••;• ^ •/'•r.vH'v'-/ 



Figure 16. Diagram of the process of fertilization in one of the lower animals. 

 A, sperms entering the outer region of the egg. B, one sperm only has entered the 

 inner part of the egg and has altered as indicated at the right. C, the nuclei of 

 sperm and egg are now similar in appearance. D, a stage of the process in which 

 the chromosomes become distinct. E, splitting of the chromosomes. F, first divis- 

 ion of the fertilized egg, with maternal and paternal chromosomes equally repre- 

 sented in the daughter cells. 



