24 The Unity of the Organism 



from it by definition. That Conklin should have been un- 

 wittingly led into this is the more surprising in that his 

 own studies, particularly those on comparative morphology 

 and physiology of the eggs of several groups of animals, 

 have added largely to the proof that many of the gross 

 attributes of the eggs themselves are subject to heredity. 

 Indeed no biologist has expressed more positively than he 

 the conception that the egg is the individual animal in one 

 of its stages of development ". . . from its earliest to its 

 latest stage an individual is one and the same organism ; 

 the Qgg of a frog is a frog in an early stage of development 

 and the characteristics of the adult frog develop out of the 



egg^ but are not transmitted through it by some 'bearer of 

 heredity.' "12 



One wonders if Conklin really would maintain that only 

 the attributes of an animal in the adult stage of its life are 

 subject to heredity; or even that the attributes of any of 

 its developmental stages are not so subject, were he con- 

 fronted with the question in this form. Although I have 

 been unable to find statements in his writings from which 

 one may positively infer what his answer would be, yet 

 several passages can be brought together which can not, I 

 believe, be harmonized with one another, but reveal real 

 contradiction. Thus in The Mechanism of Heredity, al- 

 ready cited, we find : "Differentiation, and hence heredity, 

 consists in the main in the appearance of unlike substances 

 in protoplasm and their localization in definite regions or 

 cells. Such a definition is as applicable to the latest stages 

 of differentiation, such as the formation of muscle fibers, 

 as it is to the earliest differentiations of the germ cells, 

 and the one is as truly a case of inheritance as is the other. 

 In short, different substances appear at an earlier or later 

 stage in the development of all animals, and these substances 

 A|C^ are then sorted out and localized; this is differentiation 

 ^^^Jz^Jieredity : see above]. Physiological division of labor in- 



