ed, "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. Richard sagaciously saw, as Jussieu observes, that this
genus should still be retained amongst the Malpighiaceae. 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 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 certain characters are always found correlated with others, 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 of animals all
these, the most important vital organs, are found to offer characters of
quite subordinate value.

We can see why characters derived from the embryo should be of equal
importance with those derived from the adult, for our classifications of
course include all ages of each species. 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 urged
by those great naturalists, Milne Edwards and Agassiz, that embryonic
characters are the most important of any in the classification of
animals; and this doctrine has very generally been admitted as true.
The same fact holds good with flowering plants, of which the two main
divisions have been founded on characters derived from the embryo,--on
the