37G CLASSIFICATION. CriAr. XIII. 



same order are of unequal jilijsiological importance. Any 

 number of instances could be given of the varying importance 

 for classification of the same important organ williin the same 

 group of beings. 



Agahi, no one Avill say that rudimentary or atrophied or- 

 gans are of high physiological or ^ital importance ; ^-et, un- 

 doubtedly, 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 ruminants, and certain rudimentary 

 bones of the leg, are highly serviceable in exhibiting the close 

 affinity between Ruminants and Pachyderms. Robert Brown 

 has strongly insisted on the fact that the position of the rudi- 

 mentary florets is of the highest importance in the classification 

 of the Grasses. 



Numerous instances could be given of characters derived 

 Ij-om parts which must be considered of Acry trifling physiolo- 

 gical importance, but which are universally admitted as highly 

 serviceable in the definition of Avhole groups. For instance, 

 whether or not there is an open passage from the nostrils to 

 the mouth, the only character, according to Owen, which abso- 

 lutely disting-uishcs fishes and reptiles — the inflection of the 

 angle of the jaws in ^larsupials — the manner in which the 

 wings of insects are folded — mere color in certain Alga; — mere 

 pubescence on parts of the tlower in grasses — the nature of 

 the dermal covering, as hair or feathers, in the Vertebrata. 

 If the Ornithorhyncluis 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 degree of affinity of this strange creature to birds. 



The importance, for classilication, of trifling characters, 

 mainly depends on their being correlated Avith several 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 physiological im- 

 portance and of almost universal prevalence, and A'ct leave us 

 in no doubt where it sliould be ranked. Hence, also, it has 

 been found that a classification founded on any single charac- 

 ter, however important that may be, has always failed ; for no 

 part of the organization is invariably constant. The impor- 

 tance of an aggregate of characters, even when none are im- 

 portant, alone explains the aphorism by Linuiens, naTuely, that 

 the characters do not give the genus, but the genus gives the 



