416 CLASSIFICATION. . Chap. XIII. 



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 has 

 strongly insisted on the fact that the rudimentary florets 

 are 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 physiological importance, but which are univer- 

 sally admitted as highly serviceable in the definition 

 of whole groups. For instance, whether or not there is 

 an open passage from the nostrils to the mouth, the 

 only character, according to Owen, which absolutely dis- 

 tinguishes fishes and reptiles — the inflection of the angle 

 of the jaws in Marsupials — the manner in which the 

 wings of insects are folded — mere colour 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 the Ornithorhynchus had 

 been covered with feathers instead of hair, this external 

 and trifling character would, I think, have been con- 

 sidered by naturalists as important an aid in deter- 

 mining the degree of affinity of this strange creature to 



