433 CLASSIFICATION. 



natural family, is very unequal, and in some cases seems to 

 be entirely lost." Again, in another work he says, the 

 genera of the Oonnaraceaj " differ in having one or more 

 ovaria, in the existence or absence of albumen, in the im- 

 bricate or valvular Eestivation. Any one of these charac- 

 ters singly is frequently of more than generic importance, 

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

 sufficient to separate Cnestis from Connarus." To give an 

 example among insects: in one great division of the Hy- 

 menoptera, the antennse, as Westwood has remarked,^ are 

 most constant in structure; in another division they differ 

 much, and the differences are of quite subordinate value 

 in classiiication; yet no one will say that the antennse in 

 these two divisions of the same order are of unequal physi- 

 ological 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 rudi- 

 mentary 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. Kobert 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. 



Numerous instances could be given of characters derived 

 from parts which must be considered of very trifling physi- 

 ological importance, but which are universally admitted as 

 highly servicealile in the definition of whole groujus. For 

 instance, whether or not there is an open passage from the 

 nostrils to the mouth, tlie only cliaracter, according to 

 Owen, which absolutely distinguishes fishes and reptiles^ 

 the inflection of the angle of the lower jaw in Marsupials — 

 the manner in which the wings of insects are folded — mere 

 color in certain Algae — mere pubescence on parts of the 

 flower in grasses — the nature of the dermal covering, as 

 hair or feathers, in the Vertebrata. If tlie Ornithorhyn- 

 chus had been covered with feathers instead of hair, this 

 external and trifling character would have been considered 

 by naturalists as an important aid in determining the de- 

 gree of affinity of this strange creature to birds. 



