Richard sagaciously saw, as Jussieu observes, that this
genus should still be retained among the Malpighiaceae. 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 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 be the true one; and by none more clearly
than by that excellent botanist, Aug. St. Hilaire. If several trifling
characters are always found in combination, though no apparent bond of
connexion 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 serviceable
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 Muller 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.
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