species? The question is a simple one, but the right answer to it is
hard to find, even if we appeal to those who should know most about
it. It is all those animals or plants which have descended from a
single pair of parents; it is the smallest distinctly definable group
of living organisms; it is an eternal and immutable entity; it is a mere
abstraction of the human intellect having no existence in nature. Such
are a few of the significations attached to this simple word which may
be culled from authoritative sources; and if, leaving terms and
theoretical subtleties aside, we turn to facts and endeavour to gather a
meaning for ourselves, by studying the things to which, in practice,
the name of species is applied, it profits us little. For practice
varies as much as theory. Let the botanist or the zoologist examine and
describe the productions of a country, and one will pretty certainly
disagree with the other as to the number, limits, and definitions of
the species into which he groups the very same things. In these
islands, we are in the habit of regarding mankind as of one species, but
a fortnight's steam will land us in a country where divines and
savants, for once in agreement, vie with one another in loudness of
assertion, if not in cogency of proof, that men are of different
species; and, more particularly, that the species negro is so distinct
from our own that the Ten Commandments have actually no reference to
him. Even in the calm region of entomology, where, if anywhere in this
sinful world, passion and prejudice should fail to stir the mind, one
learned coleopterist will fill ten attractive volumes with descriptions
of species of beetles, nine-tenths of which are immediately declared by
his brother beetle-mongers to be no species at all.

The truth is that the number of distinguishable living creatures almost
surpasses imagination. At least a hundred thousand such kinds of
insects alone have been described and may be identified in collections,