Seite - 228 - in The Origin of Species

a28 ORIGIN OF SPECIES 'for the welfare of the species, any slight variations which oc- curred in them would not have been accumulated and aug- mentedthrough natural selection. A structurewhichhas been developed through long-continued selection, when it ceases to be of service to a species, generally becomes variable, as we see with rudimentary organs ; for it will no longer be regu- lated by this same power of selection. But when, from the nature of the organism and of the conditions, modifications have been induced which are unimportant for the welfare of the species, they may be, and apparently often have been, transmitted in nearly the same state to numerous, otherwise modified, descendants. It cannot have been of much impor- tance to the greater number of mammals, birds, or reptiles, whether they were clothed with hair, feathers, or scales ; yet hair has been transmitted to almost all mammals, feathers to all birds, and scales to all true reptiles. A structure, what- ever it may be, which is common to many allied forms, is ranked by us as of high systematic importance, and conse- quently is often assumed to be of high vital importance to the species. Thus, as I am inclined to believe, morphological differences, which we consider as important—such as the ar- rangement of the leaves, the divisions of the flower or of the ovarium, the position of the ovules, &c.—first appeared in many cases as fluctuating variations, which sooner or later became constant through the nature of the organism and of the surrounding conditions, as well as through the inter- crossing of distinct individuals, but not through natural selec- tion; for as these morphological characters do not affect the welfare of the species, any slight deviations in them could not have been governed or accumulated through this latter agency. It is a strange result which we thus arrive at, namely that characters of slight vital importance to the spe- cies, are the most important to the systematist; but, as we shall hereafter see when we treat of the genetic principle of classification, this is by no means so paradoxical as it may at first appear. Although we have no good evidence of the existence in organic beings of an innate tendency towards progressive development, yet this necessarily follows, as I have attempted to show in the fourth chapter, through the continued action