366 CLASSIFICATION. [Chap. XIV. 



organs of reproduction, with their product the seed and embryo, are 

 of paramount importance ! 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 

 having 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, Kobert Brown, who, 

 in speaking of certain organs in the Proteaca?, says their generic 

 importance, " like that of all their parts, not only in this, but, as 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 ajstivation. Any one of these characters singly is fre- 

 quently of more than generic importance, though here even when 

 all taken together they appear insufficient to separate Cnestis from 

 Connarus." To give an example amongst insects : in one great di- 

 vision of the Hymenoptera, the antenna?, as Westwood has remarked, 

 are most constant in structure ; in another division they differ much, 

 and the differences are of quite subordinate value in classification ; 

 yet no one will say that the antenna? 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 classi- 

 fication 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 i mportance ; 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 

 serviceable in exhibiting the close affinity between ruminants and 

 pachyderms. Eobert Brown has strongly insisted on the fact that 

 the position of the rudimentary florets is of the highest importance 

 in the classification of the grasses. 



