THE PHENOMENA OF ORGANIC NATURE 103 



animals into groups, having this sort of singular subor- 

 dination one to the other, is a very remarkable circum- 

 stance ; but, as Mr. Darwin remarks, this is a result 

 which is quite to be expected, if the principles which he 

 lays down be correct. Take the case of the races which 

 are known to be produced by the operation of atavism 

 and variability, and the conditions of existence which 

 check and modify these tendencies. Take the case of the 

 pigeons that I brought before you : there it was shown 

 that they might be all classed as belonging to some one 

 of five principal divisions, and that within these divisions 

 other subordinate groups might be formed. The members 

 of these groups are related to one another in just the 

 same way as the genera of a family, and the groups them- 

 selves as the families of an order, or the orders of a class ; 

 while all have the same sort of structural relations with the 

 wild rock-pigeon, as the members of any great natural 

 group have with a real or imaginary typical form. Now, 

 we know that all varieties of pigeons of every kind have 

 arisen by a process of selective breeding from a common 

 stock, the rock-pigeon ; hence, you see, that if all species 

 of animals have proceeded from some common stock, the 

 general character of their structural relations, and of our 

 systems of classification, which express those relations, 

 would be just what we find them to be. In other words, 

 the hypothetical cause is, so far, competent to produce 

 effects similar to those of the real cause. 



Take, again, another set of very remarkable facts, 

 the existence of what are called rudimentary organs, 

 organs for which we can find no obvious use, in the par- 

 ticular animal economy in which they are found, and yet 

 which are there. 



Such are the splint-like bones in the leg of the horse, 

 which I here show you, and which correspond with bones 

 which belong to certain toes and fingers in the human 

 hand and foot. In the horse you see they are quite 

 rudimentary, and bear neither toes nor fingers ; so that 

 the horse has only one " finger " in his fore-foot and ouc 

 " toe " in his hind-foot. But it is a very curious thing 

 that the animals closely allied to the horse show more toes 

 than he ; as the rhinoceros, for instance : he has these 

 extra toes well formed, and anatomical facts show very 

 clearly that he is very closely related to the horse indeed. 

 So we may say that animals, in an anatomical sense nearly 



