Chap. XXI. NATURAL SELECTION. 211 



selection which we have seen is occasionally and uncon- 

 sciously followed by man even during the rudest periods of 

 history. 



Let us now look to the action of natural selection on special 

 characters. Although nature is difficult to resist, yet man 

 often strives against her power, and sometimes with success. 

 From the facts to be given, it will also be seen that natural 

 selection would powerfully affect many of our domestic pro- 

 ductions if left unprotected. This is a point of much interest, 

 for we thus learn that differences apparently of very slight 

 importance would certainly determine the survival of a form 

 when forced to struggle for its own existence. It may have 

 occurred to some naturalists, as it formerly did to me, that, 

 though selection acting under natural conditions would 

 determine the structure of all important organs, yet that it 

 could not affect characters which are esteemed by us of little 

 importance ; but this is an error to which we are eminently 

 liable, from our ignorance of what characters are of real value 

 to each living creature. 



TVhen man attempts to make a breed with some serious 

 defect in structure, or in the mutual relation of the several 

 parts, he will partly or completely fail, or encounter much 

 difficulty ; he is in fact resisted by a form of natural selection. 

 "We have seen that an attempt was once made in Yorkshire 

 to breed cattle with enormous buttocks, but the cows perished 

 so often in bringing forth their calves, that the attempt had 

 to be given up. In rearing short-faced tumblers, Mr. Eaton 

 says, 5 " I am convinced that better head and beak birds have 

 " perished in the shell than ever were hatched ; the reason 

 " being that the amazingly short-faced bird cannot reach and 

 " break the shell with its beak, and so perishes." Here is 

 a more curious case, in which natural selection comes into 

 play only at long intervals of time : during ordinary seasons 

 the Xiata cattle can graze as well as others, but occasionally, 

 as from 1827 to 1830, the plains of La Plata suffer from long- 

 continued droughts and the pasture is burnt up ; at such 

 times common cattle and horses perish by the thousand, but 

 many survive by browsing on twigs, reeds, &c. ; this the 

 5 ' Treatise on the Almond Tumbler,' 185.1. p. 33. 



