340 HEREDITY AND ENVIRONMENT 



salinity, pressure, temperature, etc., and these 

 modifications of the germ cells may and prob- 

 ably do lead to certain general modifications 

 of the adult, which may be larger or smaller, 

 stronger or weaker, according as the germ is 

 well or poorly nourished, etc. It is further 

 possible that these changed environmental 

 conditions may bring about such changes in 

 the structure of the germ cells as to produce 

 great and remarkable peculiarities in the 

 adult ; but it is inconceivable that the environ- 

 ment which produces rickets, or hypertrophied 

 heart, or loss of sight in one generation, should 

 modify the germ cells of the next generation 

 in such a peculiar and definite way that they 

 should give rise to these particular peculiari- 

 ties, in the absence of the extrinsic cause which 

 first produced them. The inheritance of ac- 

 quired characters is inconceivable, because 

 the egg is a cell and not an adult organism; 

 and in this case there is no sufficient evidence 

 that the thing which is inconceivable really 

 does happen. 



If environmental conditions may alter he- 

 reditary constitution we should expect to find 



