CLASSIFICATION AND ADAPTATION 37 



asked. What objection is there to the theory of 

 natural selection as an explanation of adaptations ? 

 The objection is that all the evidence goes to show 

 that the necessary variations only arose under 

 the given conditions, and, further, that the actions 

 of the conditions and the corresponding actions of 

 the organism give rise to stimuli which would 

 produce somatic modifications in the same direction 

 as the permanent modifications which have occurred. 

 My view is, then, that specific characters are usually 

 not adaptations, that other characters of taxonomic 

 value are some adaptive and some unrelated to 

 conditions of life, and that while non-adaptive 

 characters are due to spontaneous blastogenic varia- 

 tions or mutations, adaptive characters are due to 

 the direct influence of stimuli, causing somatic 

 modifications which become hereditary, in other 

 words, to the inheritance of acquired characters. 

 It has become a familiar statement that every 

 individual is the result of its heredity and its en- 

 vironment. The thesis that I desire to establish is 

 that the heredity of each individual and each type 

 is compounded of vr.riations or changes of two 

 distinct origins, one external and one internal; 

 that is to say, of variations resulting from changes 

 originating in the germ-cells or gametes, and of 

 modifications produced originally in the soma by 

 the action of external stimuli, and subsequently 

 affecting the gametes. 



When we study the characters of animals in 

 relation to sex we find that in many cases there are 

 conspicuous organs or characters present in one 

 sex, usually the male, which are absent or rudi- 

 mentary in the other. The conception of adapta- 



