INFLUENCE OF ENVIRONMENT 305 



ficial production of life is a much more diffi- 

 cult problem than was once supposed, and it 

 may be an insoluble problem. The first flush 

 of enthusiasm over experimental methods in 

 biology led to the expectation that we would 

 soon be making species and indeed whole 

 faunas and floras by the process of experi- 

 mental evolution, but the results of one or two 

 decades of such experimental work have been 

 somewhat disappointing. Inherited variations 

 do appear, incipient species arise, but there is 

 very little evidence to show that they appear 

 in response to environmental changes only. 

 Belief in the omnipotence of environment in 

 the evolution of species has steadily waned in 

 recent years, while a belief in the intrinsic 

 causes of evolution, such as the mutation 

 theory and orthogenesis, has increased. 



In ontogeny also the environmental or ex- 

 trinsic factors of development have been 

 relegated to a subordinate place, while the in- 

 trinsic or hereditary factors appear more im- 

 portant than ever. The old view that men are 

 chiefly the product of environment and train- 

 ing is completely reversed by recent studies 



