ADAPTATION 57 



only when they have assumed that structures have no utility if 

 they have been unable to detect the utility. Such exceptions are 

 extremely rare in very well-known and understood types, and 

 correspondingly more frequent in plants and animals less familiar 

 to us. We may find them in plants, insects, and molluscs, but we 

 have only to devote a moment's thought to the closely co- 

 ordinated structures and functions of such a being as man to 

 perceive how very exceptional is the exception to the rule of 

 utility. 1 



87. Adaptation must be the anchor about which the student's 

 thoughts for ever swing, the touchstone by which he must test 

 every theory of racial change and individual variation. The 

 normal individual is a bundle of adaptations. His growth, his 

 development, is nothing other than a process of individual adapta- 

 tion. Evolution is nothing other than a process of racial 

 adaptation. A theory of evolution is, or should be, nothing more 

 than an attempt to explain, or, if we prefer, summarize in brief 

 terms the processes by which adaptation is achieved. A theory of 

 heredity seeks to account for likenesses and differences between 

 parents and offspring ; if it fails to be compatible with a theory of 

 evolution which correctly interprets the facts in terms of adapta- 

 tion, it is sure to be erroneous. Many theories of heredity and 

 evolution have gone, or are going to the limbo of discarded 

 hypotheses, merely because they do not accord with the truth that 

 species are closely adapted by all or nearly all their structures and 

 functions to the environment. The plain fact that living beings 

 are able to exist is proof of adaptation. Many students of heredity 

 and evolution, especially those belonging to the experimental 

 school, will think that I put the case too strongly, but I shall 

 justify every statement up to the hilt. 



88. To be adapted to the environment in which he is produced, 

 the child must resemble the parent. The resemblance is due to 

 his recapitulation of the parental development. Presumably the 

 recapitulation occurs because the germ-plasm in the fertilized ovum 

 whence the child sprang resembled (because derived from) the 

 germ-plasm of the fertilized ovum whence the parent sprang 

 because the two portions of germ-plasm had similar hereditary 

 tendencies which were awakened by stimuli similar in kind and 

 degree. Thus half the task of the student of heredity is easily 

 accomplished. He is able in a way, superficial perhaps, but 

 valid as far as we know to account for the resemblances. Of 



* i See 648-9. 



