ii HISTORICAL ii 



related by the community of descent which the 

 accepted theory of evolution demands, though as 

 to the exact course of descent for any particular 

 group of animals there is often considerable diversity 

 of opinion. It is obvious that all this work has 

 little or nothing to do with the manner in which 

 species are formed. Indeed, the effect of Darwin's 

 Origin of Species was to divert attention from the 

 way in which species originate. At the time that it 

 was put forward his explanation appeared so satisfy- 

 ing that biologists accepted the notions of variation 

 and heredity there set forth and ceased to take any 

 further interest in the work of the hybridisers. Had 

 Mendel's paper appeared a dozen years earlier it is 

 difficult to believe that it could have failed to attract 

 the attention it deserved. Coming as it did a few 

 years after the publication of Darwin's great work, 

 it found men's minds set at rest on the problems 

 that he raised and their thoughts and energies 

 directed to other matters. 



Nevertheless, one interesting and noteworthy 

 attempt to give greater precision to the term 

 heredity was made about this time. Francis Galton, 

 a cousin of Darwin, working upon data relating to 

 the breeding of Basset hounds, found that he could 

 express on a definite statistical scheme the proportion 

 in which the different colours appeared in successive 

 generations. Every individual was conceived of as 

 possessing a definite heritage which might be ex- 

 pressed as unity. Of this, ^ was on the average 

 derived from the two parents (i.e. ^ from each parent), 

 ^ from the four grandparents, \ from the eight great- 

 grandparents, and so on. The Law of Ancestral 



