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 amoni^^ 

 members of what is, for the time being, the 



