s derived from parts which
must be considered of very trifling physiological importance, but which are
universally admitted as highly serviceable in the definition of whole
groups. For instance, whether or not there is an open passage from the
nostrils to the mouth, the only character, according to Owen, which
absolutely distinguishes fishes and reptiles--the inflection of the angle
of the jaws in Marsupials--the manner in which the wings of insects are
folded--mere colour in certain Algae--mere pubescence on parts of the flower
in grasses--the nature of the dermal covering, as hair or feathers, in the
Vertebrata. If the Ornithorhynchus had been covered with feathers instead
of hair, this external and trifling character would, I think, have been
considered by naturalists as important an aid in determining the degree of
affinity of this strange creature to {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
Malpighiaceae, 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." 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 Juss