406 CLASSIFICATION. 



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 pachy- 

 derms. Robert Brown has strongly insisted on the fact 

 that the position of the rudimentary florets is of the high- 

 est 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 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 distinguishes fishes and reptiles — the in- 

 flection 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 the Ornithorhynchus 

 had been covered with feathers instead of hair, this external 

 and trifling character would have been considered by natural- 

 ists as an important aid in determining the degree of affinity 

 of this strange creature to birds. 



The importance, for classification, of trifling characters, 

 mainly depends on their being correlated with many other 

 characters of more or less importance. The value indeed of 

 an aggregate of characters is very evident in natural history. 

 Hence, as has often been remarked, a species may depart 

 from its allies in several characters, both of high physiologi- 

 cal importance, and of almost universal prevalence, and yet 

 leave us in no doubt where it should be ranked. Hence, 

 also, it has been found that a classification founded on any 

 single character, however important that may be, has always 

 failed ; for no part of the organization is invariably constant. 1 

 The importance of an aggregate of characters, even when 

 none are important, alone explains the aphorism enunciated 

 by Linnaeus, namely, that the characters do not give the genus, 

 but the genus gives the character ; for this seems founded on 



