124 SPECIES. 



sive evolution, which is Lamarck's idea, modified by the sense 

 of the new knowledge which we have at the present day, arising, 

 on the one hand, from geology, and on the other, from philoso- 

 phical anatomy. 



Let us return to this primordial anatomical element which 

 we may call individual-element. It virtually represents a 

 vertebrate animal just as the ovum detached from the ovary 

 of the female represents a man, who is only waiting for 

 favourable circumstances in order to develope himself. This 

 individual-element, according to our hypothesis, is at first 

 simply reproduced; then, after some considerable time, its 

 descendants, will, little by little, in their own sphere of 

 activity, give birth to other elements in juxtaposition to 

 themselves, in this manner perfecting it and identifying it 

 more and more with the vertebrate type which it offers for 

 our consideration. After some considerable time vertebrates 

 of as simple an organism as mixinae and lampreys will have 

 thus appeared. Then, again, after another considerable lapse 

 of time millions of centuries, rather than thousands these 

 animals with elementary vertebra will have successively pro- 

 duced, by transformation, all the vertebrata which stock the 

 globe at the present day. 



We must here make an important remark. We have inferred 

 by all which precedes this, that the vertebrata of the present 

 day and the fossil vertebrata all descend from the same in- 

 dividual-element prototype, whose existence we have admitted. 

 In one word, we think that all the vertebrata, both present 

 and past, have the same genealogy, and are all relations. 

 That may doubtless be the case; but nothing will make us 

 admit that there once existed on our planet conditions fit for 

 the birth of this individual- element prototype, and that these 

 circumstances have never since been represented; so that the 

 most simple vertebrata of our time may very well descend from 

 a less ancient spontaneous genesis than the mammalia and 

 man himself. Nothing hinders such a supposition. It does 

 not cost us any more to admit that one day or other a simple 

 organic element is formed, endowed with a life of its own, and, 

 even more, with a latent life, which it can, by means of time 



