346 ME. G. J. EOMANES ON" PHYSIOLOGICAL SELECTIOIT. 



theory in question is released from all the difficulties whicli we 

 have been considering. For these difficulties have beset the 

 theory only because it has been made to pose as a theory of the 

 origin of species ; whereas, in point of fact, it is nothing of the 

 kind. In so far as natural selection has had anything to do with 

 the genesis of species, its operation has been, so to speak, in- 

 cidental ; it has only helped in the work of originating species 

 in so far as some among the adaptive variations which it has 

 preserved happen to have constituted differences of only specific 

 value. But there is an innumerable multitude of other such 

 diffisrences with which natural selection can have had nothing to 

 do — particularly the most general of all such differences, or that 

 of mutual sterility — while, on the other hand, by far the larger 

 number of adaptations which it has preserved are now the common 

 property of numberless species. Let it, therefore, be clearly 

 understood that it is the office of natural selection to evolve 

 adaptations — not therefore or -necessarily to evolve species. Let 

 it also be clearly understood that in thus seeking to place the 

 theory of natural selection on its true logical footing, I am in no 

 wise detracting from the importance of that theory. On the 

 contrary, I am but seeking to release it from the difficulties with 

 which it has been hitherto illegitimately surrounded*. 



Again, it is comparatively seldom that we encounter any 

 difficulty in perceiving the utilitarian significance of generic and 

 family distinctions, while we still more rarely encounter any 

 such difficulty in the case of ordinal and class distinctions. 

 Why, then, should we so often encounter this difficulty in the 



* It will be at once apparent how this release is eiFected. For, if it be 

 clearly recognized that natural selection has to do with the evolution of species 

 only in so far as specific distinctions happen to be of utilitarian character, all 

 objections to the theory raised from its inability to explain the whole origin of 

 species (or the general fact of sterility between allied species, and the frequently 

 non-utilitarian character of specific distinctions) become irrelevant ; whatever 

 its professions may have ])een, in point of fact the theory has nothing to do 

 with explaining any of these things, and, therefore, ought never to have been 

 held responsible for their explanation. Again, as regards the difficulty from 

 the overwhelming eifeets of intercrossing, this really concerns the theory of 

 natural selection only in the case of varieties ; not in that of species, genera, 

 families, &c. Yet the work of natural selection in maintaining and perfecting 

 adaptive structures in these higher taxonomic divisions is probably of quite 

 as much importance as its work in seizing upon the earliest beneficial variations, 

 although this fact has been lost sight of in the eagerness of naturalists to con- 

 stitute the theory an explanation of the origin of species. 



