84 HEREDITY AND ENVIRONMENT 



new substances and qualities, whether in the 

 organic or in the inorganic world, do not arise 

 by the gradual unfolding of what was present 

 from the beginning, but they are produced by 

 a process of "creative synthesis." 



Modern studies of germ cells have shown 

 that they are much more complex than was 

 formerly believed to be the case; they may 

 even contain different "organ-forming sub- 

 stances" which in the course of development 

 give rise to particular organs ; these substances 

 may be so placed in the egg as to foreshadow 

 the polarity, symmetry and pattern of the 

 embryo, but even the most highly organized 

 egg is relatively simple as compared with the 

 animal into which it ultimately develops. In- 

 creasing complexity, which is the essence of 

 development, is caused by the combination and 

 interaction of germinal substances under the 

 influence of the environment. The organiza- 

 tion of the oosperm may be compared to the 

 arrangement of tubes and flasks in a compli- 

 cated chemical operation; they stand in a defi- 

 nite relation to one another and each contains 

 specific substances. The final result of the 



