has unfolded some of the methods by which high
scientific results have been and may be attained, and has well
illustrated them. In a short sketch of the progress of Natural History,
he has noticed the methods which were successively pursued in its study,
and the long time which elapsed before anything like true science was
developed; he has pointed out the necessity and nature of
classification, the important terms employed, as classes, orders,
families, genera, and species, and their signification, and dwells upon
the great idea that all the denominations represented by these terms
exist definitely in Nature, and can be legitimate and permanent only as
they conform to the plan laid down by Nature herself. Much of the work
is devoted to the enforcement of this doctrine. He shows us, more
especially by the class of Radiates, how objects at first view widely
different all conform to the same definite plan, and how some which
during a part of their history would not be suspected of having any
alliance with each other, yet, by alternate generations, come to be
identical. He shows, by the ovarian egg, the great simplicity and
apparent identity of the beginnings of all animal life, and the
successive steps by which the diversified forms of animals are
developed, and insists upon the necessity of following the history of an
animal through all its phases before its true place in the grand plan
can be determined. He discusses the permanence of species, and the
limits of their variation, which he illustrates more especially by the
growth of corals, and most emphatically expresses his dissent from the
startling development-doctrines of Darwin. But it would be fruitless to
attempt an abstract of the numerous truths he has alluded to, and the
methods by which such truths are to be sought. It is to these truths, in
contradistinction to the mere study and description of species, and the
building up of systems on external characters alone, that he hopes to
direct attention. Those comprehensive truths are few. Agassiz tells us,
that, after a whole life devoted to the study of Nature, a simple
sentence may express all he himself has 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."
Though this is by no means the limit of his claim so modestly expressed,
yet that was a grand generalization, and, like the great doctrine o