No. 575] RESPONSES OF PLANTS AMD ANIMALS 659 



from being drawn from their cylindrical burrows by 

 their prey, could serve to distinguish the entire family of 

 Cicindelidce (tiger beetles). Such cases might be multi- 

 plied indefinitely. 



ticularly a zoologist, was probably (proportionately, at 

 least) less familiar with structural response phenomena. 

 He was apparently impressed with the "fixity" of the 

 so-called adaptation characters in motile animals, and 

 with the fact that they are often family, generic or specific 

 characters. With the assumption that they originated in 

 the environment in which they are now found, Darwin 

 and his followers on the zoological side credited "natural 

 selection" of structural characters with the origin of 

 species. Though broader than Lamarck, this important 

 feature of Darwin's theory was quite clearly drawn from 

 data on motile animals. After the acceptance of Darwin's 

 theory, biologists were for many years engaged in elabo- 

 rating the ideas of phylogeny and natural selection by 

 working out recapitulations and homologies and by point- 



