Chap. I.] RUDIMENTS. 31 



in my ' Origin of Species.' The homological construction 

 of the whole frame in the members of the same class is 

 intelligible, if we admit their descent from a common pro- 

 genitor, together with their subsequent adaptation to di- 

 versified conditions. On any other view the similarity of 

 pattern between the hand of a man or monkey, the foot of 

 a horse, the flipper of a seal, the wing of a bat, etc., is ut- 

 terly inexplicable. It is no scientific explanation to assert 

 that they have all been formed on the same ideal plan. 

 With respect to development, we can clearly understand, 

 on the principle of variations supervening at a rather late 

 embryonic period, and being inherited at a corresponding 

 period, ho"w it is that the embryos of wonderfully difterent 

 forms should still retain, more or less perfectly, the struct- 

 ure of their common progenitor. No other explanation 

 has ever been given of the marvellous fact that the embryo 

 of a man, dog, seal, bat, reptile, etc., can at first hardly be / 

 distinguished from each other. In order to understand 

 the existence of rudimentary organs, we have only to sup- 

 pose that a former progenitor possessed the parts in ques- 

 tion in a perfect state, and that under changed habits of 

 life they became greatly reduced, either from simple dis- 

 use, or through the natural selection of those individuals 

 which were least encumbered with a superfluous part, aided 

 by the other means previously indicated. 



Thus we can understand how it has come to pass that 

 man, and all other vertebrate animals, have been con- 

 structed on the same general model, why they pass through 

 the same early stages of development, and why they re- 

 tain certain rudiments in common. Consequently we 

 ought frankly to admit their community of descent ; to 

 take any other view, is to admit that our own structure, and 

 that of all the animals around us, is a mere snare laid to 

 entrap our judgment. This conclusion is greatly strength- 

 ened, if we look to the members of the whole animal se- 



