292 RECAPITULATION. [Chap. XV. 



the embryo of an air-breathing mammal or bird having 

 branchial slits and arteries running in loops, like those 

 of a fish which has to breathe the air dissolved in water 

 by the aid of well-developed branchiae. 



Disuse, aided sometimes by natural selection, will 

 often have reduced organs when rendered useless under 

 changed habits or conditions of life; and we can under- 

 stand on this view the meaning of rudimentary organs. 

 But disuse and selection will generally act on each crea- 

 ture, when it has come to maturity and has to play its 

 full part in the struggle for existence, and will thus have 

 little power on an organ during early life; hence the 

 organ will not be reduced or rendered rudimentary at 

 this early age. The calf, for instance, has inherited 

 teeth, which never cut through the gums of the upper 

 jaw, from an early progenitor having well-developed 

 teeth; and we may believe, that the teeth in the mature 

 animal were formerly reduced by disuse, owing to the 

 tongue and palate, or lips, having become excellently 

 fitted through natural selection to browse without their 

 aid; whereas in the calf, the teeth have been left un- 

 affected, and on the principle of inheritance at corre- 

 sponding ages have been inherited from a remote period 

 to the present day. On the view of each organism with 

 all its separate parts having been specially created, how 

 utterly inexplicable is it that organs bearing the plain 

 stamp of inutility, such as the teeth in the embryonic 

 calf or the shrivelled wings under the soldered wing- 

 covers of many beetles, should so frequently occur. 

 Nature may be said to have taken pains to reveal her 

 scheme of modification, by means of rudimentary organs, 

 of embryological and homologous structures, but we are 

 too blind to understand her meaning. 



