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THE AMERICAN NATURALIST [Vol. XLVIII 



so little known, resulted in structure in animals being fre- 

 quently regarded as fixed and every resemblance and 

 peculiarity being too often regarded as significant. The 

 explanations of supposed adaptations among animals fell 

 largely to the theory of natural selection which was 

 strained by some (see, for example, in Romanes, '92, p. 

 269) to explain origins in great detail, largely on the basis 

 of the competition of species for food, etc. Explanations 

 along this line were carried to a reductio ad absurdum as 

 indicated by Livingston ( '13) and have by no means dis- 

 appeared from the scientific calendar. This tendency 

 was less important on the plant side. More attention was 

 given to speculation concerning adaptive response. 



From a consideration of the facts just presented," we 

 note that the characters of the two leading early view 

 points in evolution were no doubt influenced if not actually 

 caused to crystallize into their peculiar form by the failure 

 of workers to recognize the entire series of phenomena 

 which we have presented above. Thus a review of the 

 responses of sessile and motile organisms throws much 

 light on the influences leading to the first conceptions and 

 later modification of these two leading doctrines. Botan- 

 ists formally years dwelt mainly on the response of sessile 

 organisms and crystallized a Lamaivkian conception of the 

 origin of adaptations through the fixing of advantageous 

 responses as hereditary characters. During the same 

 period zoologists essentially ignored sessile and other 

 multiple individualed animals and their great plasticity 

 and crystallized the Darwinian idea into Weismannian 

 germplasm doctrine based on highly specialized single 

 individualed animals. 



3. Supposed Non-Inheritance of Response and the 

 Germ Plasm Doctrine 

 The theory of the independence of the germ-plasm from 

 the soma, and its continuity from generation to genera- 

 tion, was brought strongly to the attention of zoologists 

 in 1885 by Weismann. Tt was the natural outgrowth of 

 the methods and theories of the preceding period and 



