No. 602] THE SELECTION PROBLEM 



of evidence from the work of de Vries,^! Dewar and 

 Finn,22 Bateson,^^ Lloyd,^^ and many others, showing the 

 failure of the theory of natural selection to account satis- 

 factorily for various observed happenings in evolution. 

 It is not my purpose to do this. These facts are all 

 familiar, and indeed have become commonplaces of bio- 

 logical literature. We may, however, with some chance 

 of profit try to generalize all this evidence. If we do so, 

 the writer believes that the conclusion will be reached that 

 natural selection is no longer generally regarded as the 

 primary, or perhaps even a major, factor in evolution 

 because of three general groups of facts, each well estab- 

 lished by the common observation of many biologists. 

 The first of these large facts is that all organisms possess 

 in varying, but usually very large, degree the power of per- 

 sonal, immediate, individual, somatic adaptation to the en- 

 vironment. In consequence of this power of personal adap- 

 tation the survival expectation of an individual is not gen- 

 erally and regularly a function of any static, single- valued 

 relation between its somatic structure, habits, or physi- 

 ology, on the one hand, and the impinging environmental 

 stresses on the other hand. Yet such a relation is im- 

 plicitly assumed in that part of the theory of natural selec- 

 tion which affirms a selective elimination on the basis of 

 somatic characteristics. The second broad fact is that, 

 even when selective elimination on the basis of somatic 

 characteristics does occur, it does not follow generally 

 and regularly that the somatic differences on which the 

 selection acted will reappear in the progeny, or in short be 

 inherited, actual experience having abundantly demon- 

 strated that a very great many of such somatic differences 

 are not inherited. The third large fact is that observation 

 indicates that in many cases evolutionary changes have 

 come about by relatively large, discontinuous steps, the 



21 de Vries, H., ' ' The Mutation Theory. ' ' Chicago. 



"Dewar, D., and Finn, F., "The Making of Species." London. 



"Bateson, W., "Problems of Genetics." New Haven, 1913. 



2* Lloyd, E. E., ' ' The Growth of Groups in the Animal Kingdom. ' ' Lon- 



