HEREDITY AND EVOLUTION 101 



as an exclusive one. It is certain that specific 

 factors of determination also exist in the proto- 

 plasm of the egg ; it is possible that the same may- 

 be true of the spermatozoon. Experimient has 

 demonstrated in the clearest manner that many 

 features of the early development, among them 

 some of the most important, are immediately de- 

 termined by conditions in the egg-protoplasm 

 without direct action of the nucleus. But this \ 

 fact can be rightly estimated only when the whole ! 

 genesis of the egg has been taken into account. | 

 The researches of recent years have proved that 

 the egg undergoes a long process of development 

 during its ovarian history and in the process of 

 maturation, in the course of which the greater 

 part of its protoplasmic substances are formed 

 and idtimately segregated in a particular config- 

 uration. It has thus become more than probable ! 

 that some at least of the determinative conditions j 

 in the protoplasm of the f ertihzed egg are of sec- j 

 ondary origin — ^that they are the outcome of an I 

 antecedent development in which the nucleus has i 

 played its part. Important formative protoplas- 

 mic materials are known to be of nuclear origin. 

 It is possible that all may have such an origin. 

 But even if we do not go so far as this, even if we 

 admit that the determinative factors of the nu- 

 cleus constitute but one element in an activity 

 that properly belongs to the living energid as a 

 whole, we still can not close our eyes to the plain 

 record that is written in the history of the nuclear 



