Variation and Heredity 299 



will be kept from crossing with the parent form, and since this 

 new character will be present from the beginning, the new form 

 will have much better chances of surviving than if a difference 

 in time of reaching maturity had to be gradually acquired. 



4. The new species that appear may be in some cases 

 already adapted to live, in a different environment from that 

 occupied by the parent form ; and if so, it will be isolated 

 from the beginning, which will be an advantage in avoiding 

 the bad effects of intercrossing. 



5. It is well known that the differences between related 

 species consists largely in differences of unimportant organs, 

 and this is in harmony with the mutation theory, but one of 

 the real difficulties of the selection theory. 



6. Useless or even slightly injurious characters may appear 

 as mutations, and if they do not seriously affect the perpetua- 

 tion of the race, they may persist. 



In Chapters X and XI, an attempt will be made to point 

 out in detail the advantages which the mutation theory has 

 over the Darwinian theory. 



