Chap. VI.] AFFECTED BY NATURAL SELECTION. 249 



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



