"THE ORIGIN OF SPECIES." 323 



pearance of isolation presented by various groups of 

 organic beings must be unreal. 



No part of Mr. Darwin's work ran more directly 

 counter to the prepossessions of naturalists twenty years 

 ago than this. And such prepossessions were very ex- 

 cusable, for there was undoubtedly a great deal to be 

 said, at that time, in favour of the fixity of species and 

 of the existence of great breaks, which there was no 

 obvious or probable means of filling up, between various 

 groups of organic beings. 



For various reasons, scientific and unscientific, much 

 had been made of the hiatus between man and the rest 

 of the higher mammalia, and it is no wonder that issue 

 was first joined on this part of the controversy. I have 

 no wish to revive past and happily forgotten contro- 

 versies; but I must state the simple fact that the dis- 

 tinctions in the cerebral and other characters, which 

 were so hotly affirmed to separate man from all other 

 animals in 1860, have all been demonstrated to be non- 

 existent, and that the contrary doctrine is now univer- 

 sally accepted and taught. 



But there were other cases in which the wide struct- 

 ural gaps asserted to exist between one group of ani- 

 mals and another were by no means fictitious ; and, when 

 such structural breaks were real, Mr. Darwin could ac- 

 count for them only by supposing that the intermediate 

 forms which once existed had become extinct. In a re- 

 markable passage he says 



" "We may thus account even for the distinctness of 



