374 ON THE ORIGIN OF SPECIES 



ficatory value, is almost shown by the one 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 at any group without being 

 struck with this fact ; and it has been fully acknow- 

 ledged in the writings of almost every author. It ! 

 will suffice to quote the highest authority, Robert j 

 Brown, who in speaking of certain organs in the Pro- j 

 teaceae, says their generic importance, l 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 aestivation. 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 amongst 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 classification ; yet no 

 one probably 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 

 high value in classification. No one will dispute that 

 the rudimentary teeth in the upper jaws of young rumi- 

 nants, and certain rudimentary bones of the leg, are 

 highly serviceable in exhibiting the close affinity be- 

 tween Ruminants and Pachyderms. Robert Brown ha* 

 strongly insisted on the fact that the rudimentary florets 

 are of the highest importance in the classification of tha 

 Grasses. 



