CLASSIFICATION 376 



Numerous instances could be given of characters 

 derived from parts which must be considered of very 

 trifling 1 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 

 birds and reptiles, as an approach in structure in any one 

 internal and important organ. 



The importance, for classification, of trifling charac- 

 ters, mainly depends on their being correlated with 

 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 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 organisation is universally 

 constant. The importance of an aggregate of characters, 

 even when none are important, alone explains, I think, 

 that saying of Linnaeus, that the characters do not give 

 the genus, but the genus gives the characters ; for this 

 saying seems founded on an appreciation of many 

 trifling points of resemblance, too slight to be defined. 

 Certain plants, belonging to the Malpighiaceae, bear 

 perfect and degraded flowers ; in the latter, as A. de 

 Jussieu has remarked, ' the greater number of the 



