112 THE GENESIS OF SPECIES. [CHAP. 



We have here no action, of " Natural Selection ; " it was 

 not that cextain puppies happened accidentally to be 

 capable of enduring more rarefied air, and so survived, but 

 the offspring were directly modified by the action of sur- 

 rounding conditions. Neither was the change elaborated 

 by minute modifications in many successive generations, 

 but appeared at once in the second. 



Further, with regard to sudden alterations of form, 

 Nathusius is said to state positively as to pigs, 1 that the 

 result of common .experience and of his experiments was 

 that rich and abundant food, given during youth, tends by 

 some direct action to make the head broader and shorter. 

 Curious jaw appendages often characterize Normandy pigs, 

 according to M. Eudes Deslongchamps. Eichardson figures 

 these appendages on the old " Irish greyhound pig," and 

 they are said by Nathusius to appear occasionally in 

 all the long-eared races. Mr. Darwin observes, 2 " As no 

 wild pigs are known to have analogous appendages, we 

 have at present no reason to suppose that their appearance 

 is due to reversion ; and if this be so, we are forced to 

 admit that somewhat complex, though apparently useless 

 structures may be suddenly developed without the aid of 

 selection." Again, " Climate directly affects the thickness 



those of the men on the high plateau ; whilst their femora had become 

 somewhat lengthened, as had their tibiae, but in a less degree." Here the 

 rapidity of the change only two generations points rather to a direct 

 action of conditions than to that of "Natural Selection." In favour of 

 direct modification, another passage from Mr. Darwin may be quoted. He 

 says, ' ' In young persons whose heads from disease have become fixed 

 either sideways or backways, one of the eyes has changed its position, 

 and the bones of the skull have been modified." Descent of Man, vol. i. 

 p. 147. 



1 "Animals and Plants under Domestication," vol. i. p. 72. 



2 Ibid. p. 76. 



