OBJECTIONS TO THE THEORY OF DESCENT. 341 



cetaceans, "and to constitute connecting links with the 

 aquatic carnivore." 



Even the Avide interval between birds and reptiles 

 has been shown by the naturalist just quoted to be par- 

 tially bridged over in the most unexpected manner, on 

 the one hand, by the ostrich and extinct Archeopteryx, 

 and on the other hand, by the Compsognathus, one of 

 the dinosaurians — that group which includes the most 

 gigantic of all terrestrial reptiles. Turning to the In- 

 vertebrata, Barrande asserts, and a higher authority could 

 not be named, that he is every day taught that, although 

 palaeozoic animals can certainly be classed under existing 

 groups, yet that at this ancient period the groups were 

 not so distinctly separated from each other as they now 

 are. 



Some writers have objected to any extinct species, or 

 group of species, being considered as intermediate be- 

 tween any two living species or groups of species. If by 

 this term it is meant that an extinct form is directly in- 

 termediate in all its characters between two living forms 

 or groups, the objection is probably valid. But in a 

 natural classification many fossil species certainly stand 

 between living species, and some extinct genera between 

 living genera, even between genera belonging to distinct 

 families. The most common case, especially with respect 

 to very distinct groups, such as fish and reptiles, seems 

 to be that, supposing them to be distinguished at the 

 present day by a score of characters, the ancient members 

 are separated by a somewhat lesser number of characters ; 

 so that the two groups formerly made a somewhat nearer 

 approach to each other than they now do. 



