ns, in the Cow the horn is
hollow, and remains through life firmly attached to the bone, while in the
Deer it is solid and is shed every year. With these facts before us, we
cannot hesitate to place the Dog, the Cat, and the Bear in one division,
as carnivorous animals, and the other three in another division as
herbivorous animals,--and looking a little farther, we perceive, that, in
common with the Cow and the Deer, the Goat and the Sheep have cloven feet,
and that they are all ruminants, while the Horse has a single hoof, does
not ruminate, and must therefore be separated from them, even though, like
them, he is herbivorous.

This is but the simplest illustration, taken from the most familiar
objects, of this comparative method; but the same process is equally
applicable to the most intricate problems in animal structures, and will
give us the clue to all true affinities between animals. The education of
a naturalist, now, consists chiefly in learning how to compare. If he have
any power of generalization, when he has collected his facts, this habit
of mental comparison will lead him up to principles, to the great laws of
combination. It must not discourage us, that the process is a slow and
laborious one, and the results of one lifetime after all very small. It
might seem invidious, were I to show here how small is the sum total of
the work accomplished even by the great exceptional men, whose names are
known throughout the civilized world. But I may at least be permitted to
speak of my own efforts, and to sum up in the fewest words the result of
my life's work. I have devoted my whole life to the study of Nature, and
yet a single sentence may express all that I have done. I have shown that
there is a correspondence between the succession of Fishes in geological
times and the different stages of their growth in the egg,--this is all.
It chanced to be a result that was found to apply to other groups and has
led to other conclusions of a like nature. But, such as it is, it has been
reached by this system of comparison, which, though I speak of it now in
its application to the study of Natural History, is equally important in
every other branch of knowledge. By the same process the most mature
results of scientific research in Philology, in Ethnology, and in Physical
Science are reached. And let me say that the community should foster the
purely intellectual efforts of scientific men as carefully as they do
their elemen