HEREDITY AND ADAPTATION. 15 



it was impossible to understand and interpret aright this 

 remarkable resemblance. Darwin's greatest merit is that 

 he has now enabled us to understand this circumstance. 

 This gifted naturalist was the first to place the pheno- 

 mena of Heredity on the one hand, and of Adaptation on 

 the other, in their true light, and to show the fundamental 

 significance of their constant interaction in the production 

 of organic forms. He was the first to point out the im- 

 portant part played by the continual Struggle for Existence 

 in which all organisms take part, and how under its in- 

 fluence, through Natural Selection, new species of organisms 

 have arisen, and still arise, entirely by the interaction of 

 Heredity and Adaptation. Darwin thus enabled us properly 

 to understand the immensely important relation existing 

 between the two divisions of the History of Evolution : 

 Ontogeny, and Phylogeny. 



If the phenomena of Heredity and Adaptation are left 

 unnoticed, if these two formative physiological functions of 

 the organism are not taken into account, then it is entirely 

 impossible thoroughly to understand the History of Evolution; 

 so that before the time of Darwin we had no clear idea of 

 the real nature and causes of the development of germs. 

 It was utterly impossible to explain the strange series of 

 forms through which a human being passes in its embryonic 

 evolution ; it was impossible to comprehend the reason of 

 the curious series of various animal-like forms which appear 

 in the Ontogeny of man. Previously it was even generally 

 believed that the whole human being, with all its parts 

 foreshadowed, existed even in the egg, and that his evolution 

 was only an unfolding of the form, a simple process of 

 growth. But this is not at all the case. On the contrary, 



