exist. They are, however, represented in these regions by very closely
allied, but distinct forms--the 'Homarus Americanus' and the 'Homarus
Capensis': so that we may say that the European has one species of
'Homarus'; the American, another; the African, another; and thus the
remarkable facts of geographical distribution begin to dawn upon us.

Again, if we examine the contents of the earth's crust, we shall find in
the latter of those deposits, which have served as the great burying
grounds of past ages, numberless lobster-like animals, but none so
similar to our living lobster as to make zoologists sure that they
belonged even to the same genus. If we go still further back in time,
we discover, in the oldest rocks of all, the remains of animals,
constructed on the same general plan as the lobster, and belonging to
the same great group of 'Crustacea'; but for the most part totally
different from the lobster, and indeed from any other living form of
crustacean; and thus we gain a notion of that successive change of the
animal population of the globe, in past ages, which is the most
striking fact revealed by geology.

Consider, now, where our inquiries have led us. We studied our type
morphologically, when we determined its anatomy and its development,
and when comparing it, in these respects, with other animals, we made
out its place in a system of classification. If we were to examine
every animal in a similar manner, we should establish a complete body of
zoological morphology.

Again, we investigated the distribution of our type in space and in
time, and, if the like had been done with every animal, the sciences of
geographical and geological distribution would have attained their
limit.