374 THE ORIGIN OF SPECIES 



essential character." With plants how remarkable it is that the 

 organs of vegetation, on which their nutrition and life depend, 

 are of little signification; whereas the organs of reproduction, 

 with their product the seed and embryo, are of paramount im- 

 portance! So again, in formerly discussing certain morphological 

 characters which are not functionally important, we have seen 

 that they are often of the highest service in classification. This 

 depends on their constancy throughout many allied groups; and 

 their constancy chiefly depends on any slight deviations not hav- 

 ing been preserved and accumulated by natural selection, which 

 acts only on serviceable characters. 



That the mere physiological importance of an organ does not 

 determine its classificatory value, is almost proved by the fact, 

 that in allied groups, in which the same organ, as we have every 

 reason to suppose, has 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 certain organs in the Proteaceae, says 

 their generic importance, "like that of all their parts, not only in 

 this, but, as I apprehend, in every natural family, is very un- 

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

 another work he says, the genera of the Connaracese "differ in 

 having one or more ovaria, in the existence or absence of albumen, 

 in the imbricate or valvular aestivation. Any one of these char- 

 acters singly is frequently of more than generic importance, 

 though here, even when all taken together, they appear insuffi- 

 cient to separate Cnestis from Connarus." To give an example 

 among insects: in one great division of the Hymenoptera, the 

 antennse, as Westwood has remarked, are most constant in struc- 

 ture; in another division they differ much, and the differences are 

 of quite subordinate value in classification; yet no one will say 

 that the antennae in these two divisions of the 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, 



