308 MI8CELLANE0UB OBJECTIONS TO THE 



becomes variable, as we see with rudimentary organs; for 

 it will no longer be regulated by this same power of selec- 

 tion. 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 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 result which we thus 

 arrive at, namely, that characters of slight vital importance to 

 the species, 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 Jio means so paradoxi- 

 cal as it may at first appear. \ 



Although we have no good evidence of the existence 

 in organic beings of an innate tendency toward progressive 

 development, yet this necessarily follows, as I have attempt- 

 ed to show in the fourth chapter, through the continued 

 action of natural selection. For the best definition which 

 has ever been given of a high standard of organization, is 

 the degree to which the parts have been specialized or dif- 

 ferentiated; and natural selection tends toward this end, 

 inasmuch as the parts are thus enabled to perform their 

 functions more efficiently. 



