Page - 455 - in The Origin of Species

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 ofmany triflingpoints 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