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- 

 mented through natural selection. A structure which has 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 



