DIFFICULTIES OF THE THEORY 275 



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 in- 

 crease 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 unknown 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 ignorance of the precise cause of the slight analogous 

 differences between true species. 



Utilitarian Doctrine^ liow far true: Beauty^ hovj 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 

 beauty, to delight man or the Creator (but this latter 

 point is beyond the scope of scientific discussion), or for 



