IV.] MINUTE MODIFICATIONS. 119 



ject ; for that any very appreciable gain to the individual 

 can have resulted from the slightly lessened degree 

 of required nourishment thence resulting (i.e. from the 

 suppression), seems to us to be an almost absurd pro- 

 position." * 



HAND OF THE POTTO (PERODICTICUS), FROM LIFE. 



Again to anticipate somewhat, the great group of whales 

 (Cetacea) was fully developed at the deposition of the 

 Eocene strata. On the other hand, we may pretty safely 

 conclude that these animals were absent as late as the 

 latest secondary rocks, so that their development could 

 not have been so very slow, unless geological time is 

 (although we shall presently see there are grounds to 

 believe it is not) practically infinite. It is true that it is 

 generally very unsafe to infer the absence of any animal 

 forms during a certain geological period because no 

 remains of them have as yet been found in the strata 

 then deposited : but in the case of the Cetacea it is safe 

 to do so ; for, as Sir Charles Lyell remarks, 2 they are 

 animals the remains of which are singularly likely to 

 have been preserved had they existed, in the same way 



1 " Anatomy of the Lemuroidea." By James Murie, M.D., and St. George 

 Mivart. Trans. Zool. Soc., March 1866, p. 91. 



2 " Principles of Geology," last edition, vol. i. p. 163. 



