3IO THE HISTORY OF CEEATION. 



hy the laii's of inheritance and adaptation ; by tribe I 

 mean the ancestors which form the chain of progenitors of 

 the individual concerned. (Gen. Morph. ii. p. 110-147, 371.) 

 In this intimate connection of ontogeny and phylogeny, I 

 see one of the most important and irrefutable proofs of the 

 Theory of Descent. No one can explain these phenomena 

 unless he has recourse to the laws of Inheritance and 

 Adaptation; by these alone are they explicable. These 

 laws, which we have previously explained, are the laws of 

 abbreviated, of honiochronic, and of homotojnc inheritance, 

 and here deserve renewed consideration. As so high and 

 complicated an organism as that of man, or the organism of 

 every other mammal, rises upwards from a simple cellular 

 state, and as it progresses in its differentiation and per- 

 fecting it passes through the same series of transform- 

 ations which its animal progenitors have passed through, 

 during immense spaces of time, inconceivable ages ago. I 

 have already pointed out this extremely important parallel- 

 ism of the development of individuals and tribes (p. 10). 

 Certain very early and low stages in the development of 

 man, and the other vertebrate animals in general, correspond 

 completely in many points of structure with conditions 

 which last for life in the lower fishes. The next phase 

 which follows upon this presents us with a change of the 

 fish-like being into a kind of amphibious animal At a later 

 period the mammal, with its special characteristics, de- 

 velops out of the amphibian, and we can clearly see, in the 

 successive stages of its later development, a series of steps of 

 progressive transformation which evidently correspond with 

 the difterences of different mammalian orders and families. 

 Now, it is precisely in the same succession that we also see 



