ctive. We think that Professor Huxley, in his anxiety to avoid the
error of making Thought the measure of Things, does not sufficiently
bear in mind the fact, that as our notion of necessity is determined by
some absolute uniformity pervading all orders of our experiences, it
follows that an organic correlation which cannot be conceived otherwise,
is guaranteed by a much wider induction than one ascertained only by the
observation of organisms. But the truth is, that there are relatively
few organic correlations of which the negation is inconceivable. If we
find the skull, vertebrae, ribs, and phalanges of some quadruped as large
as an elephant; we may indeed be certain that the legs of this quadruped
were of considerable size--much larger than those of a rat; and our
reason for conceiving this correlation as necessary, is, that it is
based, not only upon our experiences of moving organisms, but upon all
our mechanical experiences relative to masses and their supports. But
even were there many physiological correlations really of this order,
which there are not, there would be danger in pursuing this line of
reasoning, in consequence of the liability to include within the class
of truly necessary correlations, those which are not such. For instance,
there would seem to be a necessary correlation between the eye and the
surface of the body: light being needful for vision, it might be
supposed that every eye must be external. Nevertheless it is a fact that
there are creatures, as the _Cirrhipedia_, having eyes (not very
efficient ones, it may be) deeply imbedded within the body. Again, a
necessary correlation might be assumed between the dimensions of the
mammalian uterus and those of the pelvis. It would appear impossible
that in any species there should exist a well-developed uterus
containing a full-sized foetus, and yet that the arch of the pelvis
should be too small to allow the foetus to pass. And were the only
mammal having a very small pelvic arch, a fossil one, it would have been
inferred, on the Cuvierian method, that the foetus must have been born
in a rudimentary state; and that the uterus must have been
proportionally small. But there happens to be an extant mammal having an
undeveloped pelvis--the mole--which presents us with a fact that saves
us from this erroneous inference. The young of the mole are not born
through the pelvic arch at all; but in front of it! Thus, granting that
some quite _direct_ physiolo