Chap. XIII. CLASSIFICATION. 417 



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

 internal and important organ. 



The importance, for classification, of trifling characters, 

 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 Malpighiacese, bear perfect and de- 

 graded 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." But 

 when Aspicarpa produced in France, during several 

 years, only degraded flowers, departing so wonderfully 

 in a number of the most important points of structure 

 from the proper type of the order, yet M. Eichard 

 sagaciously saw, as Jussieu observes, that this genus 

 should still be retained amongst the Malpighiacese. 

 This case seems to me well to illustrate the spirit with 

 which our classifications are sometimes necessarily 

 founded. 



Practically when naturalists are at work, they do 



T 3 



