I . ON A PIECE OF CHALK 35 



identically the same as those which lived in the 

 times called " older tertiary," which succeeded the 

 cretaceous epoch ; and the crocodiles of the older 

 tertiaries are not identical with those of the 

 newer tertiaries, nor are these identical with 

 existing forms. I leave open the question whether 

 particular species may have lived on from epoch 

 to epoch. But each epoch has had its peculiar 

 crocodiles; though all, since 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 ? 

 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 pre-existing 

 form by the operation of natural causes. Choose 

 your hypothesis ; I have chosen mine. I can find 

 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 the writer of Genesis records the pro- 

 ceedings of the fifth and six days of the Creation. 



On the other hand, I see no good reason for 

 doubting the necessary alternative, that all these 

 varied species have been evolved from pre-existing 



D 2 



