EVOLUTION IN NATURE 171 



result in a multiplication of portions of chromo- 

 somes, or chromosome numbers may be multiplied, 

 or individual genes may undergo change. All of 

 these things result in mutations, or in characters 

 which are different from the preexisting state, but 

 they are no more than a modification or a loss. 

 The idea has been seriously advanced that evolu- 

 tion is due to mutant losses, but it has received 

 little support and is apparently worthy of no more. 

 Losses have played their part, but like all other 

 limited factors, they cannot be extended to explain 

 the whole process of evolution. 



One possibility suggests itself as an explanation 

 of mutation by the addition of new things, viz., 

 that the variation of association in the individual 

 between heritage and environment may sometimes 

 bring about conditions which enable the genes 

 themselves to change. Guyer has cited a very in- 

 teresting chemical action which illustrates this 

 possibility. "... when hydrochloric acid is passed 

 into an alcoholic solution of hydrocyanic acid, 

 provided there are suflficient quantities of these 

 three ingredients, five definite crystalline end- 

 products of their interaction result. First the 

 hydrochloric and hydrocyanic acids combine to 

 form amidoformyl-chloride, which then adds an- 

 other molecule of hydrocyanic acid. This product 

 next reacts with one molecule of alcohol which to 

 this point has been inactive. The result is what 



