ON A PIECE OF CHALK 75 



vast antiquity. They abounded ages before the chalk was 

 deposited; they throng the rivers in warm climates, at the 

 present day. There is a difference in the form of the joints 

 of the backbone, and in some minor particulars, between the 

 crocodiles of the present epoch and those which lived before 5 

 the chalk; but, in the cretaceous epoch, as I have already 

 mentioned, the crocodiles had assumed the modern type of 

 structure. Notwithstanding this, the crocodiles of the chalk 

 are not identically the same as those which lived in the times 

 called " older tertiary/' which succeeded the cretaceous 10 

 epoch ; and the crocodiles of the older tertiaries are not identi- 

 cal with those of the newer tertiaries, nor are these identical 

 with existing forms. I leave open the question whether par- 

 ticular species may have lived on from epoch to epoch. But 

 each epoch has had its peculiar crocodiles ; though all, since 15 

 the chalk, have belonged to the modern type, and differ 

 simply in their proportions, and in such structural particulars 

 as are discernible only to trained eyes. 



How is the existence of this long succession of different 

 species of crocodiles to be accounted for ? 20 



Only two suppositions seem to be open to us either each 

 species of crocodile has been specially created, or it has 

 arisen out of some preexisting form by the operation of natu- 

 ral causes. 



Choose your hypothesis ; I have chosen mine. I can find 25 

 no warranty for believing in the distinct creation of a score 

 of successive species of crocodiles in the course of countless 

 ages of time. Science gives no countenance to such a wild 

 fancy ; nor can even the perverse ingenuity of a commentator 

 pretend to discover this sense, in the simple words in which 30 

 the writer of Genesis records the proceedings of the fifth and 

 sixth days of the Creation. 



On the other hand, I see no good reason for doubting the 

 necessary alternative, that all these varied species have 



