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 Kuminants and Pachyderms. Eobert Brown has 
strongly insisted on the fact that the rudimentary fiorets 
are of the highest importance in the classification of the 
Grrasses. 
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 
Algse—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 
