est the book find much of
it a sort of intellectual pemmican--a mass of facts crushed and pounded
into shape, rather than held together by the ordinary medium of an
obvious logical bond; due attention will, without doubt, discover this
bond, but it is often hard to find.

Again, from sheer want of room, much has to be taken for granted which
might readily enough be proved; and hence, while the adept, who can
supply the missing links in the evidence from his own knowledge,
discovers fresh proof of the singular thoroughness with which all
difficulties have been considered and all unjustifiable suppositions
avoided, at every reperusal of Mr. Darwin's pregnant paragraphs, the
novice in biology is apt to complain of the frequency of what he fancies
is gratuitous assumption.

Thus while it may be doubted if, for some years, any one is likely to be
competent to pronounce judgment on all the issues raised by Mr. Darwin,
there is assuredly abundant room for him, who, assuming the humbler,
though perhaps as useful, office of an interpreter between the 'Origin
of Species' and the public, contents himself with endeavouring to
point out the nature of the problems which it discusses; to distinguish
between the ascertained facts and the theoretical views which it
contains; and finally, to show the extent to which the explanation it
offers satisfies the requirements of scientific logic. At any rate, it
is this office which we purpose to undertake in the following pages.

It may be safely assumed that our readers have a general conception of
the nature of the objects to which the word "species" is applied; but it
has, perhaps, occurred to a few, even to those who are naturalists 'ex
professo', to reflect, that, as commonly employed, the term has a double
sense and denotes two very different orders of relations. When we call a
group of animals, or of plants, a species, we may imply thereby, either
that all these animals or plants have some common peculiarity of form
or structure; or, we may mean that they possess some common functional
character. That part of biological science which deals with form
and structure is called Morphology--that which concerns itself with
function, Physiology--so that we may conveniently speak of these two
senses, or aspects, of "species"--the one as morphological, the other
as physiological. Regarded from the former point of view, a species
is nothing more than a kind of animal or plant, which is distinctly