1890 ON PHYSIOLOGICAL SELECTION 249 



next generation. And since the ova are among the 

 earliest formed tissues, the first-cross creature is 

 born more or less infertile — its sexual condition comes 

 straight from its mother — and acts back on its mother 

 by natural selection, as a man's books act back on 

 him when he is considered as a factor in the making 

 of English style. 



It is an advantage then (from the point of view 

 of life and death in the long run) for a mother to bear 

 fertile extreme forms, and infertile central forms — and 

 this in any degree. 



There might be five mares. The first indifferently 

 bearing to all alike, and so on an average bearing 

 equal numbers [the rest bearing increasingly less 

 freely with B], ten A and ten AB, eleven A and nine 

 AB, twelve A and eight AB [and so on] . . . nine- 

 teen A and one AB, twenty A and no AB. 



All the AB's are at a disadvantage, and must in 

 long run be unrepresented in the final balance of 

 species. 



And if there are two which bear equally AB's, 

 the one which bears them most infertile will in the 

 long run be best represented in the aggregate of; 

 descendants from herself and her relations. 



Geanies, Eosshire, N.B. : July 28, 1890. 



My dear Waggett, — It seems to me most desirable 

 to retain the term ' natural selection ' as defined and 

 everywhere used by Darwin. I know that it is 

 often (and not rarely, unconsciously as by Wallace) 



