232 MENDELISM 



on the Mendelian theory of inheritance when applied 

 to populations. These figures are calculated on the 

 supposition that there is random mating of the parents, 

 but if there were a tendency for like to mate with like 

 the correlation values would become still higher. Yule 

 therefore concludes that ' there is therefore no diffi- 

 culty in account ing for a coefficient of 0*5 on the 

 theory of segregation, but such a value probably 

 indicates an absence of the somatic phenomenon of 

 dominance. In the case of characters like stature, 

 span, etc., in man this does not seem very improb- 

 able.' 



It is impossible to bring the present chapter to a con- 

 clusion without some reference to the practical aspects 

 of the Mendelian discovery. The progress of experi- 

 mental research in this field during the last few 

 years has been so rapid, that there is little ground for 

 astonishment in the fact that only a small proportion 

 of those to whom the discovery of the Mendelian 

 method is of the very highest importance from a com- 

 mercial point of view have yet arrived at any serious 

 appreciation of it. The improvement of the breeds of 

 cultivated plants and domestic animals is a subject of 

 vital importance to the whole human race, quite apart 

 from the question of the commercial profit which it 

 represents for those whose business it is to be directly 

 concerned with the process the actual plant- and 

 animal-breeders themselves. 



Hitherto the methods of amelioration which have 

 been adopted have depended largely upon guess-work, 



