President's Address. 149 



An opportunity for this kind of selection to come into 

 operation would only occur to the varieties not eliminated 

 by environmental selection, the struggle with other organisms, 

 the struggle for food, the struggle against heat and cold, 

 floods and tempests, and all the other trials which have to 

 be faced before maturity is reached. 



It is needless to say that the survivors of the struggle with 

 the environment would in most cases show a very consider- 

 able amount of variation, for it is not accurate to say that 

 environmental selection results in the survival of the fittest, 

 and ruthlessly eliminates everything that fails to pass the 

 test of utility; at the most the environment eliminates the 

 unfit. As a matter of fact, most environments are wonder- 

 fully tolerant, and capable, as a rule, of sustaining many 

 different varieties and species of both plants and animals. 



Hence, though many promising varieties succumb before 

 they are old enough to breed — are eliminated by environ- 

 mental selection, a considerable number survive and do their 

 best to originate new species. Of the survivors from the 

 struggle with the environment it is impossible to forecast 

 their future. Again and again I have failed to preserve 

 striking and interesting variations. I have had rabbits 

 without a tail, rabbits which were wont to spin like Japanese 

 dancing mice, and dwarf rabbits with legs bent like a 

 Dachshund, but in each case I failed, as breeders say, to fix 

 the type. These and other failures led to the inquiry. Why 

 are some sports inherited, e.g., the habit of pacing in horses, 

 while others have only a transitory existence ? The answer 

 to this important question is, I believe, that variations are 

 qualitative as well as quantitative, physiological as well as 

 morphological. Hitherto, as far as I can gather, attention 

 has been mainly, if not entirely, directed to the mor- 

 phological or structural aspect of variations. That they 

 require to be considered from a physiological as well as a 

 morphological standpoint will, I think, be at once admitted. 

 By intercrossing, some variations are at once swamped, but 

 others persist unaltered. That one variation is inherited 

 while another is lost must be due to some subtle difference 

 in the germ-plasm from which they spring. Though it may 



