IV.] MINUTE MODIFICATIONS. 113 



by the first. Thus " Sir Charles Lyell mentions that some 

 Englishmen, engaged in conducting the operations of the 

 Real del Monte Company in Mexico, carried out with them 

 some greyhounds, of the best breed, to hunt the hares which 

 abound in that country. It was found that the greyhounds 

 could not support the fatigues of a long chase in this at- 

 tenuated atmosphere, and, before they could come up with 

 their prey, they lay down gasping for breath ; but these 

 same animals have produced whelps, which have grown up, 

 and are not in the least degree incommoded by the want 

 of density in the air, but run down the hares with as much 

 ease as do the fleetest of their race in this country." ' 



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

 was not that certain 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. 



With regard once more to sudden alterations of form, 

 Nathusius is said to state positively as to pigs, 6 that the re- 

 sult 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. Curi- 

 ous jaw appendages often characterize Normandy pigs, ac- 

 cording to M. Eudes Deslongchamps. Richardson 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, 7 " As no wild pigs 

 are known to have analogous appendages, we have at pres- 

 ent no reason to suppose that their appearance is due to 



5 Carpenter's " Comparative Physiology," p. 987, quoted by Mr. J. J. 

 Murphy, " Habit and Intelligence," vol. i., p. 171. 



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

 7 Ibid., p. 76. 



