168 FOSSIL REPTILES. 



we find a regular number, the same for all species, with indeed 

 some very rare exceptions. 



It was a curious question to find out whether this analogy 

 was sustained in the other classes of the vertebralia, and if the 

 differences which they exhibit might not depend upon the 

 periods in which their bones became inter-cemented ; if the 

 reptiles, for instance, which always preserve many more su- 

 tures in the head than the mammifera, might be considered 

 in this respect as mammifera, in a state analogous to that of the 

 foetus ; if the birds, which, in their early age, have as many as the 

 reptiles, but which, when they approach the adult state, often 

 exhibit less than the mammifera, might be considered, on the 

 contrary, as mammifera passing rapidly from one state to the 

 other, and even going beyond this last, in reference to the union 

 of their bones. 



M. Geoffroy St. Hilaire was one of the first to consider 

 this interesting problem ; and in many particulars he has 

 treated it with signal success. The Baron has also considered 

 it several times in the course of his lectures, and on other 

 occasions. But many other profound anatomists, especially 

 certain of the German school, have made it the object of more 

 consecutive researches and detailed examinations. 



These writers have not only endeavoured to assign to each 

 bone in the oviparous vertebralia its correspondence with some 

 bone, or determined portion of a bone in the mammifera, but, 

 following the ideal and pantheistic system of metaphysics, 

 termed the philosophy of nature, which has for some time 

 prevailed very much in Germany, and the language of which 

 has been adopted in the positive sciences, they have endea- 

 voured to find in the head a representation of the totahtyof the 

 body, as in general, according to the principles of this philo- 

 sophy, each part, and each part of a part, should always repre- 

 sent the whole. 



Thus M. Oken, in his programma on the signification of the 

 heady has proceeded from the analogy which exists, in many 



