242 Animal Life and Intelligence. 



on the body are transmissible believe also that the effects 

 of use and disuse are transmissible. 



The vital vigour of the organism is a determining con- 

 dition of importance. The vital vigour of males has 

 favoured the origin of secondary sexual characters ; that of 

 females, the fostering and protection of young, and therefore 

 the development in them of vifcal vigour. 



The almost universally admitted factor in guidance is 

 natural selection. But we must be careful not to use it 

 as a mere formula. 



Whether sexual selection is also a factor is still a matter 

 of opinion. Without it the specific character and constancy 

 of secondary sexual features are at present unexplained. 

 If inherited use and disuse are admitted as factors in 

 origin, they must also be admitted as important factors in 

 guidance. 



Questions of origin and guidance should, so far as is 

 possible, be kept distinct. These terms, however, apply to 

 the origin and guidance of variations. In the origin of 

 species guidance is a factor, no doubt a most important 

 factor. The title of Darwin's great work was, therefore, 

 perfectly legitimate. And those who say that natural 

 selection plays no part in the origin of species are, there- 

 fore, undoubtedly in error. 



