BIOLOGICAL EVOLUTION 73 



The knowledge and use of the Mendelian law by animal 

 breeders and horticulturists during the past few years have shown 

 its great importance to man in the process of active material 

 adaptation, and its present use in studies of defectiveness has 

 demonstrated its value in eugenics which comes under the division 

 of active social adaptation. 



Before summing up the contributions of biology to sociology 

 and to the subject of this book in particular it may not be amiss to 

 consider briefly the position of biologists today on some of the 

 fundamental questions brought out in our survey of the theories 

 of Darwin and his successors. For this purpose the Centennial 

 Addresses in Honor of Charles Darwin before the American 

 Association for the Advancement of Science, should furnish 

 impartial material. 



That inborn variation and natural selection alone are suflScient 

 was questioned by J. M. Coulter of the University of Chicago 

 from the side of botany. David Starr Jordan of Leland Stanford 

 emphasized isolation as a factor of equal importance with natural 

 selection. E. B. Wilson of Columbia showed that experiments 

 had proven the possibiHty of the transmission of ontogenetic 

 variations and gave assent to the theory of metabolism through 

 chemical action. " Experiment," he said, " has established the 

 fact that certain forms of development are thus controlled by 

 substances, the ' hormones,' that may be extracted from the 

 cells that produce them, and upon injection into the body call 

 forth their characteristic results. Such an eJffect, for instance, is 

 the development of the cock's comb in the hen upon injection of 

 testic-extract and its recession to the characteristic female condi- 

 tion upon cessation of the injections." ^ Professor Wilson made 

 another statement of great suggestive value in its bearing on social 

 progress: " We must not forget that some of the most acute and 

 thoughtful of naturalists have in recent years expressed the 

 conviction that the ultimate control of development is not to be 

 sought in the physico-chemical properties of the germ cells, but 

 in an indwelling * entelechy ' or * elan de la vie,' a power of 



1 Fifty Years of Darwinism, pp. io6, 107. 



