prevailing phases of thought on some biological questions.

The great master in whose dissecting rooms I was privileged to work held
that species were not permanent as a fact established inductively on a
wide basis of observation, by which comparative osteology had been
created. Camper and Hunter suspected the species might be transitory;
but Cuvier, in defining the characters of his anaplotherium and
palaeotherium, etc., proved the fact. Of the relation of past to present
species, Cuvier had not an adequate basis for a decided opinion.
Observation of changes in the relative position of land and sea
suggested to him one condition of the advent of new species on an island
or continent where old species had died out. This view he illustrates by
a hypothetical case of such succession, but expressly states: "I do not
assert that a new creation was necessary to produce the species now
existing, but only that they did not exist in the same regions, and must
have come from elsewhere." Geoffrey Saint Hilaire opposed to Cuvier's
inductive treatment of the question the following expression of belief:
"I have no doubt that existing animals are directly descended from the
animals of the antediluvian world," but added, "it is my belief that the
season has not yet arrived for a really satisfying knowledge of
geology."

The main collateral questions argued in their debates appeared to me to
be the following:

Unity of plan or final purpose, as a governing condition of organic
development?

Series of species, uninterrupted or broken by intervals?

Extinction, cataclysmal or regulated?

Development, by epigenesis or evolution?

Primary life, by miracle or secondary law?

Cuvier held the work of organisation to be guided and governed by final
purpose or adaptation. Geoffrey denied the evidence of design and
contended for the principle which he called "unity of composition," as
the law of organisation. Most of his illustrations were open to the
demonstration of inaccuracy; and the language by which disciples of the
kindred school of Schelling illustrated in the animal structure the
transcendental idea of the whole in every part seemed little better than
mystical jargon. With Cuvier, answerable parts occurred in the
zoological scale because they had to perform similar functions.

As, however, my observations and comparisons accumulated, they enforced
a reconsideration of Cuvier's conclusions. To demonstrate the evidence
of the