Influence of Environment 207 



2. Present Emphasis on Heredity. On the other hand modern 

 studies in genetics are emphasizing the immense, the overwhelm- 

 ing importance of heredity, in both phylogeny and ontogeny. No 

 one now takes seriously the assertion that life can be experi- 

 mentally produced at the present time from non-living matter. It 

 is evident that the artificial production of life is a much more 

 difficult problem than was once supposed, and it may be an in- 

 soluble problem. The first flush of enthusiasm over experimental 

 methods in biology led to the expectation that we would soon be 

 making species by the process of experimental 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 and at 

 present we have no means of controlling such variations. 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 ortho- 

 genesis, has increased. 



In ontogeny also the environmental or extrinsic factors of de- 

 velopment have been relegated to a subordinate place, while the 

 intrinsic or hereditary factors appear more important than ever. 

 The old view that men are chiefly the product of environment and 

 training is completely reversed by recent studies of heredity. The 

 modifications which may be produced by environment and educa- 

 tion are small and temporary as compared with those which are 

 determined by heredity. 



3. Both Indispensable. These conclusions are, in the main, 

 well founded. The evidence of the tremendous importance of 

 heredity is so complete that we may rest assured that thinking 

 men will never again return to the position which prevailed until 

 a few years ago regarding the all-importance of environment. 

 And yet there is danger of going too far in the opposite direction. 

 Neither environment nor heredity is all-important, but both are 

 necessary to development. The germ cells with all their inherent 



