character are constant in individuals of both sexes, so far as
observation has reached; and that they are not due to domestication or
to artificially superinduced external circumstances, or to any outward
influence within his cognizance; that the species is wild, or is such
as it appears by Nature."

[footnote] *On the Osteology of the Chimpanzees and Orangs:
Transactions of the Zoological Society, 1858.

If we consider, in fact, that by far the largest proportion of recorded
existing species are known only by the study of their skins, or bones,
or other lifeless exuvia; that we are acquainted with none, or next to
none, of their physiological peculiarities, beyond those which can be
deduced from their structure, or are open to cursory observation; and
that we cannot hope to learn more of any of those extinct forms of life
which now constitute no inconsiderable proportion of the known Flora
and Fauna of the world: it is obvious that the definitions of these
species can be only of a purely structural, or morphological, character.
It is probable that naturalists would have avoided much confusion of
ideas if they had more frequently borne the necessary limitations of
our knowledge in mind. But while it may safely be admitted that we are
acquainted with only the morphological characters of the vast majority
of species--the functional or physiological, peculiarities of a few have
been carefully investigated, and the result of that study forms a large
and most interesting portion of the physiology of reproduction.

The student of Nature wonders the more and is astonished the less, the
more conversant he becomes with her operations; but of all the
perennial miracles she offers to his inspection, perhaps the most
worthy of admiration is the development of a plant or of an animal from