262 PROBLEMS OF FERTILIZATION 



nature as to start or accelerate the chemical processes 

 underlying development the connection between mem- 

 brane formation and causation of development would 

 become intelligible." This idea seems to me to be 

 entirely consistent with the fertilizin hypothesis. This 

 substance, which is contained in the cortex, may be 

 conceived as exerting a ferment-hke action as it pene- 

 trates into the egg or is carried in by the spermatozoon, 

 though this conception must remain for the present 

 hypothetical. It corresponds to what I have called 

 elsewhere (1914) binding of the ovophile group of the 

 fertilizin. 



2. The internal changes. — The problem of the in- 

 ternal events of activation presents two aspects: first, 

 that of change in metabolism evidenced by increased 

 oxygen consumption in some cases, by initiation of 

 development in all cases; and second, the problem of 

 proper co-ordination of the karyokinesis of the first 

 cleavage. Under the first head it would seem that all 

 degrees of activation are possible up to the optimum, 

 which in this case appears to correspond with the max- 

 imum, for we do not know any cases in which defects 

 in the induced development are due to excessive acti- 

 vation, i.e., to too rapid rate of the processes activated 

 or initiated. As we have seen, polyspermy does not 

 induce such a condition; its evil effects result from 

 other causes; neither does excessive action of partheno- 

 genetic agents cause an excessive increase in rate of 

 metabolic activities, but rather a decreased rate. It is 

 possible to grade the action of parthenogenetic agents 

 to various degrees of activation; beginning, for in- 

 stance, with the production of membrane formation 



