DESCENT OF MAN FROM SOME LOWER FORM. 135 



serves notice that it is of no importance to a yery young 

 animal, as long as it remains in its mother's womb or in 

 the egg, or as long as it is nourished and protected by its 

 parent, whether most of its characters are acquired a 

 little earlier or later in life. It would not signify, for in- 

 stance, to a bird which obtained its food by having a 

 much-curved beak whether or not while young it pos- 

 sessed a beak of this shape, as long as it was fed by its 

 parents. 



I have stated in the first chapter that at whatever age 

 a variation first appears in the parent, it tends to reappear 

 at a corresponding age in the offspring. Certain varia- 

 tions can only appear at corresponding ages ; for instance, 

 peculiarities in the caterpillar, cocoon, or imago states 

 of the silk-moth ; or, again, in the full-grown horns of 

 cattle. But variations, which, for all that we can see, 

 might have first appeared either earlier or later in life, 

 likewise tend to reappear at a corresponding age in the 

 offspring and parent. I am far from meaning that this 

 is invariably the case, and I could give several exceptional 

 cases of variations (taking the word in the largest sense) 

 which have supervened at an earlier age in the child than 

 in the parent. 



These two principles, namely, that slight variations 

 generally appear at a not very early period of life, and are 

 inherited at a corresponding not early period, explain, as 

 I believe, all the above specified leading facts in embry- 

 ology. 



EMBETOLOGT AGAINST ABRUPT CHANGES. 



Ori^n of Unless we admit transformations as pro- 



Species, digious as those advocated by Mr. Mivart, such 

 page 203. ^^ ^j^^ sudden development of the wings of 

 birds or bats, or the sudden conversion of a Hipparion 



