76 VIGNETTES FROM NATURE. 



others like the Irish elk and the mammoth 

 belong to the very latest geological period ; 

 and yet others, though of somewhat higher 

 antiquity like the animals of the Paris basin 

 have left representatives nearly, if not quite, 

 as big as themselves. The teeth of what 

 seems to have been the biggest known fish 

 a prodigious shark are dredged up among 

 the modern ooze of the Pacific ; and though 

 no individuals quite large enough to have 

 owned them have ever been observed, yet 

 people who believe in the sea-serpent may 

 well expect one to turn up in the flesh at 

 some future period, while even more sceptical 

 persons must still admit that they have 

 become extinct at a very late date. 



The explanation of the existence and 

 extinction of extremely large animals in each 

 group seems to be this. As a whole, evolu- 

 tion appears to tend towards an increase of 

 size in some members at least of every class. 

 But this increase is most noticeable among 

 members of what is, for the time being, the 



