216 THE ORIGIN OF SPECIES 



nearly the same physiological value, its classificatory 

 value is widely different. No naturalist can have worked 

 long at any group without being struck with this fact; 

 and it has been fully acknowledged in the writings of 

 almost every author. It will suffice to quote the highest 

 authority, Robert Brown, who, in speaking of certtiin 

 organs in the Proteaceae, says their generic importance, 

 "like that of all their parts, not only in this, but, a« I 

 apprehend, in every natural family, is very unequal, and 

 in some cases seems to be entirely lost." Again, in 

 another work, he says the genera of the Connaraceae 

 "differ in having one or more ovaria, in the existence or 

 absence of albumen, in the imbricate or valvular aestiva- 

 tion. Any one of these characters singly is frequently of 

 more than generic importance, though here even when 

 all taken together they appear insufficient to separate 

 Cnestis from Connarus." To give an example among 

 insects: in one great division of the Hymenoptera, the 

 antennae, as Westwood has remarked, are most constant 

 in structure; in another division they differ much, and 

 the differences are of quite subordinate value in classifi- 

 cation; yet no one will say that the antennae in these two 

 divisions of tlie same order are of unequal physiological 

 importance. Any number of instances could be given of 

 the varying importance for classification of the same 

 important organ within the same group of beings. 



Again, no one will say that rudimentary or atrophied 

 organs are of high physiological or vital importance; yet, 

 undoubtedly, organs in this condition are often of much 

 value in classification. No one will dispute that the 

 rudimentary teeth in the upper jaws of young ruminants, 

 and certain rudimentary bones of the leg, are highly 



