Theories of Chemical Development 149 



peculiarity in a definite part of the organism, if it does not 

 seem quite impossible, certainly seems difficult to con- 

 ceive. It is true that these theories of the Spencer type 

 can always bring up the objection that to a visible varia- 

 tion of a certain group of cells there might possibly cor- 

 respond similar variations in all the other cells of the 

 organism, but always so small that they are not appre- 

 ciable. But such an explanation of the especially inherit- 

 able variations would be formal rather than actual. 



This applies equally well, it may here be said paren- 

 thetically, to evolutionary theories without preformed 

 germs, such for example as the theories which are called 

 those of the chemical development of the egg. They start 

 out usually with a heterogeneous germ substance, con- 

 stituted by multiple and diverse chemical substances, from 

 chemical interactions of which new chemical compounds 

 are formed later, which give place in their turn, in each 

 cell as in a separate crucible independent of the others, 

 to new chemical reactions and consequently to new com- 

 pounds different in the different cells, and so on up to the 

 end of development. But one cannot conceive how each 

 one of these components of the germ substance, which 

 commences to exercise its chemical action upon the other 

 constituents from the very first moment of development, 

 even though it be the only point in which one germ differs 

 from another, can bring about an alteration of the or- 

 ganism limited to a single point rather than an alteration 

 extended over the entire organism. 



The argument brought up by the partisans of pre- 

 formistic germs, both epigenesists and preformationists 

 properly so called, is then really weighty enough to force 

 us to hold as inadmissible every biogenetic hypothesis 

 which starts out from or is based upon a homogeneous 



