the
writings of almost every author. It will suffice to quote the highest
authority, Robert Brown, who, in speaking of certain organs in the
Proteaceae, says their generic importance, "like that of all their
parts, not only in this, but, as I apprehend in every natural family,
is very unequal, and in some cases seems to be entirely lost." Again,
in another work he says, the genera of the Connaraceae "differ in having
one or more ovaria, in the existence or absence of albumen, in the
imbricate or valvular aestivation. Any one of these characters singly is
frequently of more than generic importance, though here even, when
all taken together, they appear insufficient to separate Cnestis from
Connarus." To give an example among insects: in one great division
of the Hymenoptera, the antennae, as Westwood has remarked, are most
constant in structure; in another division they differ much, and the
differences are of quite subordinate value in classification; yet no one
will say that the antennae in these two divisions of the same order are
of unequal physiological importance. Any number of instances could be
given of the varying importance for classification of the same important
organ within the same group of beings.

Again, no one will say that rudimentary or atrophied organs are of high
physiological or vital importance; yet, undoubtedly, organs in this
condition are often of much value in classification. No one will dispute
that the rudimentary teeth in the upper jaws of young ruminants,
and certain rudimentary bones of the leg, are highly serviceable in
exhibiting the close affinity between Ruminants and Pachyderms. Robert
Brown has strongly insisted on the fact that the position of the
rudimentary florets is of the highest importance in the classification
of the Grasses.

Numerous instances could be given of characters 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 lower jaw 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