CHAPTER V 



THE PHYSIOLOGY OF FERTILIZATION 

 I. INTRODUCTION 



It is commonly said that there are two main problems 

 in the physiology of fertilization, viz. : the initiation of 

 development, or activation, and biparental inheritance; 

 but these are more properly results of fertilization. In- 

 deed so long as we regard fertilization primarily as a 

 function of prospective significance in the life of the 

 organism we shall miss the more specific aspects of the 

 process. Once fertilization is accomplished development 

 and inheritance may be left to look after themselves. 



Fertilization must be regarded as a reaction possess- 

 ing very definite biological and biochemical characters. 

 But it is not a single reaction in either a biological or 

 chemical sense; it is rather a series of reactions which 

 cannot be regarded as complete until full capacity for 

 development and inheritance is attained by the zygote. 

 Fertilization may therefore be partial, which may be 

 indicated by early cessation of the developmental pro- 

 cess or deficiency of developmental energy. It is obvi- 

 ous that partial fertilization will furnish an important 

 means of analysis. 



The reactions of fertilization form an irreversible 

 series, though it is conceivable that some of them taken 

 singly may be reversible. Spermatozoa have no effect on 

 already fertilized eggs and do not penetrate into them; 

 this condition arises very early in the fertilization 



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