H THE DESCENT OF MAN. 



have all been formed on the same ideal plan. With respect to 

 development, we can clearly understand, on the principle of varia- 

 tions supervening at a rather late embryonic period, and being 

 inherited at a corresponding period, how it is that the embryos 

 of wonderfully different forms should still retain, more or less 

 perfectly, the structure of their common progenitor. No other 

 explanation has ever been given of the marvelous fact that the 

 embryos of a man, dog, seal, bat, reptile, &o., can at first hardly 

 be distinguished from each other. In order to understand the 

 existence of rudimentary organs, we have only to suppose that a 

 former progenitor possessed the parts in question in a perfect 

 state, and that under changed habits of life they became greatly 

 reduced, either from simple disuse, or through the natural selec- 

 tion 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 constructed on the same 

 general model, why they pass through the same early stages of 

 development, and why they retain 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 struc- 

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

 to entrap our judgment. This conclusion is greatly strengthened, 

 if we look to the members of the whole animal series, and con- 

 sider the evidence derived from their affinities or classification, 

 their geographical distribution and geological succession. It is 

 only our natural prejudice, and that arrogance which made our 

 forefathers declare that they were descended from demi-gods, 

 which leads us to demur to this conclusion. But the time will be- 

 fore long come, when it will be thought wonderful that naturalists, 

 who were well acquainted with the comparative structure and de- 

 velopment of man, and other mammals, should have believed that 

 each was the work of a separate act of creation. 



ciples In accordance with their uses. No one has shown so well, how 

 admirably such structures are adapted for their iinal purpose; and 

 this adaptation can, as I believe, be explained through natural selection. 

 In considering the wing of a bat, he brings forward (p. 218) what ap- 

 pears to me (to use Auguste Comte's words) a mere metaphysical 

 principle namely, the preservation "in its integrity of the mammalian 

 "nature of the animal." In only a few cases does he discuss rudiments, 

 and then only those parts which are partially rudimentary, such as the 

 little hoofs of the pig and ox, which do not touch the ground; these 

 he shows clearly to be of service to the animal. It is unfortunate that 

 he did not consider such cases as the minute teeth, which never cut 

 through the jaw in the ox, or the mammae jof male quadrupeds, or tht 

 wings of certain beetles, existing under the soldered wing-covers, or 

 the vestiges of the pistil and stamens in various flowers, and many 

 other such cases. Although I greatly admire Prof. Bianooni's work 

 yet the belief now held by most naturalists seems to me left unshaken! 

 that homological structures are intxplicable on the principle of mer6 

 adaptation. 



