CLASSIFICATION 455 



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 classification, of trifling characters, 

 mainly depends on their being correlated with many other 

 characters of more or less importance. The value indeed of 

 an aggrjgate 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 organisation is invariably constant. 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 characters ; for this seems founded 

 on the appreciation of many trifling points of resemblance, too 

 slight to be defined. Certain plants, belonging to the Mal- 

 pighiaceae, bear perfect and degraded flowers; in the latter, 

 as A. de Jussieu has remarked, "the greater number of the 

 characters proper to the species, to the genus, to the family, 

 to the class, disappear, and thus laugh at our classification." 

 When Aspicarpa produced in France, during several years, 

 only these degraded flowers, departing so wonderfully in a 

 number of the most important points of structure from the 

 proper type of the order, yet M. Richard sagaciously saw, 

 as Jussieu observes, that this genus should still be retained 

 amongst the Malpighiacese. This case well illustrates the 

 spirit of our classifications. 



Practically, when naturalists are at work, they do not 

 trouble themselves about the physiological value of the char- 

 acters which they use in defining a group or in allocating any 

 particular species. If they find a character nearly uniform, 

 and common to a great number of forms, and not common 

 to others, they use it as one of high value; if common to 

 some lesser number, they use it as of subordinate value. This 

 principle has been broadly confessed by some naturalists to 



