600 THE ORIGIN OF SPECIES 



tions which occurred in them would oot have been 

 accumulated and augmented 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 regulated 

 by this same power of selection. But when, from the 

 nature of the organism and of the conditions, modifica- 

 tions 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 importance to the greater number 

 of mammals, birds, or reptiles, whether they were clothed 

 with hair, feathers, or scales; yet hair has been trans- 

 mitted to almost all mammals, feathers to all birds, and 

 scales to all true reptiles. A structure, whatever it may 

 be, which is common to many allied forms, is ranked by 

 us as of high systematic importance, and consequently 

 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 

 arrangement of the leaves, the divisions of the flower or 

 of the ovarium, the position of the ovules, etc. — 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 intercrossing of distinct individuals, but 

 not through natural selection ; 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 



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