224 HABIT AND INTELLIGENCE. [chap. 



though different in species, from those which now inhabit 



the same region. The same is true of the wingless birds 



Resem- of New Zealand. And it is a general fact in geology, that 



blance of ^|^g fossil species of two strata, lying conformably one on 



species m ■*■ ' ./ o j 



conform- the other, present a strong resemblance even where they 



a e s ra a. ^^^ ^^^^ identical. The inference is obvious, though I do 

 not say certain, that when we thus find the same area to 

 have been inhabited, in two successive geological periods, 

 by similar though different species, the connexion between 



Connexion them is that of descent. I say that, at the present stage of 

 y escent, ^|^g argument, I do not regard this conclusion as proved. 

 I believe I shall give ample proof of it before I have com- 

 j)leted this work. I must, however, mention that when 

 I speak of the newer set of species as connected with the 

 older by the bond of descent, I do not mean direct descent 

 like that by which we are connected with the races of men 

 that inhabited the British Islands a thousand years ago : I 



but modi- mean descent modified in a peculiar way, which I shall 

 have to explain in another chapter. 



But it may be urged, that Cuvier's principle of the 

 perfect adaptation of the organism to the conditions of its 

 existence may, after all, account for the facts of both the 

 geographical and the geological distribution of species. It 

 may be urged that we do not really know enough on the 

 subject of the relation of the structure and characters of 

 any species to the conditions of its life to assert that the 

 one cannot be determined by the other. In a great variety 

 of cases, the connexion is obvious enough ; as, for instance, 

 in the adaptation of the monkey's hand or the woodpecker's 

 foot to a life spent in cKmbing trees. But where the con- 

 nexion is not obvious, we have no right to infer that it 

 does not exist. The more we know concerning the subject 

 of the complex relations between organisms and the con- 

 ditions of their lives, the more intricate do these relations 

 appear. Darwin has insisted on this with great force, and 

 with all his accustomed lucidity. 



I reply to this argument, that it is refuted by evidence 

 identical in kind with the evidence of experiment. There 

 are a great many instances of organisms being introduced 



