146 THE GENESIS OF SPECIES. [CHAP. 



absent, but they are absent in cases where we might cer- 

 tainly a priori have expected them to be present. 



Now it has been said: 1 "If Mr. Darwin's theory be 

 true, the number of varieties differing one from another 

 a very little must have been indefinitely great, so great 

 indeed as probably far to exceed the number of individuals 

 which have existed of any one variety. If this be true, 

 it would be more probable that no two specimens pre- 

 served as fossils should be of one variety than that we 

 should find a great many specimens collected from a very 

 few varieties, provided, of course, the chances of preserva- 

 tion are equal for all individuals." " It is really strange 

 that vast numbers of perfectly similar specimens should 

 be found, the chances against their perpetuation as fossils 

 are so great ; but it is also very strange that the specimens 

 should be so exactly alike as they are, if, in fact, they 

 came and vanished by a gradual change." 



Mr. Darwin attempts 2 to show cause why we should 

 believe a priori that intermediate varieties would exist in 

 lesser numbers than the more extreme forms ; but though 

 they would doubtless do so sometimes, it seems too much 

 to assert that they would do so generally, still less univer- 

 sally. Now little less than universal and very marked 

 inferiority in numbers would account for the absence of 

 certain series of minutely intermediate fossil specimens. 

 The mass of palaeontological evidence is indeed over- 

 whelmingly against minute and gradual modification. It 

 is true that when once an animal has obtained powers of 

 flight its means of diffusion are indefinitely increased, and 

 we might expect to find many relics of an aerial form and 



1 North British Review, New Series, vol. vii., March 1867, p. 317. 



2 "Origin of Species," 5th edition, 1869, p. 212. 



