IV.] MINUTE MODIFICATIONS. Ill 



sandy-coloured fur." l The conditions of life seem to pro- 

 duce a considerable effect on horses, and instances are 

 given by Mr. Darwin of pony breeds 2 having independently 

 arisen in different parts of the world, possessing a certain 

 similarity in their physical conditions. Also changes due 

 to climate may be brought about at once in a second 

 generation, though no appreciable modification is shown 

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

 Englishmen, engaged in conducting the operations of the 

 Eeal 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 attenuated 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." 3 



1 "Animals and Plants under Domestication," vol. i. p. 47. 



2 Ibid. p. 52. 



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

 Murphy, " Habit and Intelligence," vol. i. p. 171. Mr. Darwin, in his 

 " Descent of Man," vol. i. p. 119, mentions that certain South American 

 Indians (Aymaras), inhabiting a lofty region, have remarkably long bodies 

 and short legs especially the femora. He adds: "These men are so 

 thoroughly acclimatized to their cold and lofty abode, that when carried 

 down by the Spaniards to the low eastern plains, and when now tempted 

 down by high wages to the gold-washings, they suffer a frightful rate of 

 mortality. Nevertheless, Mr. Forbes found a few pure families which had 

 survived during two generations ; and he observed that they still in- 

 herited their characteristic peculiarities. But it was manifest, even with- 

 out measurement, that these peculiarities had all decreased ; and, on 

 measurement, their bodies were found not to be so much elongated as 



