Characters as Adaptive and Specific. 163 



and thus the theory of natural selection becomes 

 a theory of the origin of genera, of families, of orders, 

 and of classes, quite as much as it is a theory of the 

 origin of species. In other words, it is everywhere 

 a theory of adaptations ; and it is only where 

 the adaptations happen to be restricted to single 

 species that the theory therefore and incidentally 

 becomes also a theory of the particular species which 

 presents them. Hence it is by no means the same 

 proposition to affirm that the theory of natural 

 selection is a theory of the origin of species, and 

 that it is a theory of the origin of adaptations, as 

 some of my critics have represented it to be ; for 

 these two things are by no means conterminous. 

 And in as far as the two propositions differ, it is 

 perfectly obvious that the latter is the true one. 



Possibly, however, it may be said Assuredly natural 

 selection is a theory of the origin (i. e. cumulative 

 development) of adaptations; and, no less assuredly, 

 although species owe their origin to such adaptations, 

 there is now no common measure between these two 

 things, seeing that in numberless cases the same 

 adaptations are the common property of numberless 

 species. But, allowing all this, we must still remember 

 that in their first beginnings all these adaptations must 

 have been distinctive of, or peculiar to, some one par- 

 ticular species, which afterwards gave rise to a whole 

 genus, family, order, or class of species, all of which 

 inherited the particular adaptations derived from 

 this common ancestor, while progressively gaining 

 additional adaptive characters severally distinctive of 

 their subsequently diverging lines of descent So 

 that really all adaptive characters must originally 

 M a 



