100 DARWINISM CHAP. 



been able to increase them to a marvellous extent by the 

 simple process of always preserving the best varieties to breed 

 from. Along with these larger variations others of smaller 

 amount occasionally appeal', sometimes in external, sometimes 

 in internal characters, the very bones of the skeleton often 

 changing slightly in form, size, or number ; but as these 

 secondary characters have been of no use to man, and have 

 not been sjoecially selected by him, they have, usually, not 

 been developed to any great amount except Avhen they have 

 been closely dependent on those external characters which he 

 has largely modified. 



As man has considered only utility to himself, or the 

 satisfaction of his love of beauty, of novelty, or merely of 

 something strange or amusing, the variations he has thus pro- 

 duced have something of the character of monstrosities. Not 

 only are they often of no use to the animals or plants them- 

 selves, but they are not unfrequently injurious to them. In 

 the Tumbler pigeons, for instance, the habit of tumbling is 

 sometimes so excessive as to injure or kill the bird ; and many 

 of our highly-bred animals have such delicate constitutions 

 that they are very liable to disease, while their extreme 

 peculiarities of form or structure Avould often render them 

 quite unfit to live in a wild state. In plants, many of our 

 double flowers, and some fruits, have lost the power of pro- 

 ducing seed, and the race can thus be continued only by means 

 of cuttings or grafts. This jDeculiar character of domestic 

 productions distinguishes them broadly from wild species and 

 varieties, which, as will be seen by and by, are necessarily 

 adapted in every part of their organisation to the conditions 

 under which they have to live. Their importance for our 

 present inquiry depends on their demonstrating the occurrence 

 of incessant slight variations in all parts of an organism, with 

 the transmission to the oflfspring of the special characteristics 

 of the parents ; and also, that all such slight variations are 

 capable of being accumulated by selection till they present 

 very large and important divergencies from the ancestral 

 stock. 



We thus see, that the evidence as to variation afforded 

 by animals and plants iinder domestication strikingly accords 

 ■with that which we have 2:)roved to exist in a state of nature. 



