ONTOGENESIS 197 



relatively specialized condition. There is a striking 

 parallel in the course of the differentiating process 

 in the ontogenesis of all species. The similarity 

 of the steps in any two different forms is in direct 

 ratio to the closeness of their relationship. Sexual 

 reproduction (by gametes) is apparently an inci- 

 dental specialization and not a necessity for the 

 accomplishment of the reproduction process, since 

 experiment has shown that the egg contains within 

 itself all the required potentialities for individual 

 development. It is probable that the same would 

 be also true of the sperm except that specialization 

 has deprived the latter of the necessary food supply 

 to serve as a source of energy. The accomplishment 

 of the specific form is not only brought about by the 

 differentiation of a specialized cell, normally pro- 

 duced by another individual (ontogenesis), but also 

 is manifest in the restoration of structures in the 

 same individual, when these are abnormally altered 

 or destroyed (restitution). 



