AFFECTED BY NATURAL SELECTION. 189 



different climates. With cattle susceptibility to the attacks 

 of flies is correlated with color, as is the liability to be pois- 

 oned by certain plants; so that even color would be thus 

 subjected to the action of natural selection. Some observ- 

 ers are convinced that a damp climate affects the growth 

 of the hair, and that with the hair the horns are corre- 

 lated. Mountain breeds always differ from lowland 

 breeds; and a mountainous country would probably 

 affect the hind limbs from exercising them more, and 

 possibly even the form of the pelvis; and then by the 

 law of homologous variation, the front limbs and the head 

 would probably be affected. The shape, also, of the pelvis 

 might affect by pressure the shape of certain parts of the 

 young in the womb. The laborious breathing necessary in 

 high regions tends, as we have good reason to believe, to 

 increase the size of the chest; and again correlation would 

 come into play. The effects of lessened exercise, together 

 with abundant food, on the whole organization is probably 

 still more important; and this, as H. von Nathusius has 

 lately shown in his excellent Treatise, is apparently one 

 chief cause of the great modification which the breeds of 

 swine have undergone. But we are far too ignorant to 

 speculate on the relative importance of the several known 

 and unknow^n causes of variation; and I have made these 

 remarks only to show that, if we are unable to account for 

 the characteristic differences of our several domestic breeds, 

 which nevertheless are generally admitted to have arisen 

 through ordinary generation from one or a few parent- 

 stocks, we ought not to lay too much stress on our ignor- 

 ance of the precise cause of the slight analogous differences 

 between true species. 



UTILITARIAN" DOCTRINE, HOW FAR TRUE: BEAUTY, HOW 



ACQUIRED. 



The foregoing remarks lead me to say a few words on 

 the protest lately made by some naturalists against the 

 utilitarian doctrine that every detail of structure has been 

 produced for the good of its possessor. They believe that 

 many structures have been created for the sake of beautv, 

 to delight man or the Creator (but this latter point is be- 

 yond the scope of scientific discussion), or for the sake of 



