NATURAL SELECTION 99 



attained, it may be lost through a slackening of Natural Selec- 

 tion, and still more through a total cessation of it. But we are 

 trying to find proof that a cessation of selection may lead to 

 something more than instability ; that it may lead to the large 

 reduction or loss of characters in all the individuals of a race or 

 species. 



If pammixis really produces the great results that Weismann 

 attributes to it, we ought to find evidence among our domestic 

 animals. We must be careful, however, to give the principle 

 fair play, and it is certainly not fair to take such a case as that 

 of the brain of domestic ducks and say that since they are not 

 selected for intelligence, as their wild progenitors to a great 

 extent were, their brain ought by now to have been reduced to 

 something very small. What we do find is that in the wild duck 

 (Anas boscas) the brain is nearly twice as heavy in proportion to the 

 body. 1 But the domestic duck of most breeds is much bigger 

 and heavier than its wild kinsman ; the increase has extended 

 even to its wing-bones, though powerful legs, to carry its great 

 bulk, are the special features developed. 2 In those breeds in 

 which the weight of the body is more than double that of the 

 wild mallard, it cannot be said that there has been absolute re- 

 duction of brain, if it is found that its relative weight has been 

 reduced to half. The brain has not increased as the body has 

 increased ; that is all. This would certainly be a defeat for 

 pammixis if absolute pammixis had been at work. But there 

 has been nothing more than a slackening of Natural Selection, 

 not a total cessation of it. There is no harm in a domestic duck 

 being an imbecile compared with her wild kinsfolk, but absolute 

 idiocy would be fatal. She could not recognise the call of the 

 farmer's wife at feeding time, could not forage for herself as 

 tame ducks are still bound to do. It might be thought that her 

 wings would have become mere vestiges since it is much better 

 that she should be quite incapable of flight. But the flight 

 muscles form the meat on the breast ; a deficiency there would 



1 See Lloyd Morgan's Animal Life and Intelligence, p. 171. He quotes Sir J. 

 Crichton Browne. 



2 Darwin : Animalt and Plants under Domestication, vol. i. p. z8$. 



