CLASSIFICATION. 407 



the appreciation of many trifling points of resemblance, too 

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

 pighiacese 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 

 among the Malpighiaeeae. 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 

 characters which they use in defining a group or in allocat- 

 ing 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 com- 

 mon to some lesser number, they use it as of subordinate 

 value. This principle has been broadly confessed by some 

 naturalists to be the true one ; and by none more clearly than 

 by that excellent botanist, Aug. Saint-Hilaire. If several 

 trifling characters are always found in combination, though 

 no apparent bond of connection can be discovered between 

 them, especial value is set on them. As in most groups of 

 animals, important organs, such as those for propelling the 

 blood, or for aerating it, or those for propagating the race, 

 are found nearly uniform, they are considered as highly ser- 

 viceable in classification ; but in some groups all these, the 

 most important vital organs, are found to offer characters of 

 quite subordinate value. Thus, as Fritz Miiller has lately 

 remarked, in the same group of crustaceans, Cypridina is 

 furnished with a heart, while in two closely allied genera, 

 namely Cypris and Cytherea, there is no such organ ; one 

 species of Cypridina has well-developed branchiae, while 

 another species is destitute of them. 



We can see why characters derived from the embryo 

 should be of equal importance with those derived from the 

 adult, for a natural classification of course includes all ages. 

 But it is by no means obvious, on the ordinary view, why the 

 structure of the embryo should be more important for this 

 purpose than that of the adult, which alone plays its full 

 part in the economy of nature. Yet it has been strongly 



