2o8 PRIMARY FACTORS OF ORGANIC EVOLUTION. 



sharks, and in but few other respects. But the im- 

 portance of this consideration must be seen from the 

 fact that it is on single characters of this kind that the 

 divisions of the zoologist depend. Hence we can say 

 truly that one order is identical with an incomplete 

 stage of another order, though the species of the one 

 may never at the present time bear the same relation 

 in their entirety to the species of the other. Still more 

 frequently can we say that such a genus is the same in 

 character as a stage passed by the next higher genus ; 

 but when we can say this of species, it is because their 

 distinction is almost gone. It will then depend on the 

 opinion of the naturalist as to whether the repressed 

 characters are permanent or not. Parallelism is then 

 reduced to this definition : that each separate charac- 

 ter of every kind, which we find in a species, repre- 

 sents a more or less complete stage of the fullest 

 growth of which the character appears to be capable. 

 In proportion as those characters in one species are 

 contrasted with those of another by reason of their 

 number, by so much must we confine our comparison 

 to the characters alone, and the divisions they repre- 

 sent; but when the contrast is reduced by reason of 

 the fewness of differing characters, so much the more 

 truly can we say that the one species is really a sup- 

 pressed or incomplete form of the other The denial 

 of this principle by the authorities cited has been in 

 consequence of this relation having been assigned to 

 orders and classes, when the statement should have 

 been confined to single characters, and divisions char- 

 acterized by them. There seems, however, to have 

 been a want of exercise of the classifying quality or 

 power of ' abstraction ' of the mind on the part of the 

 objectors." 



