change. Here we have a picture of progressive evolution that carries
with it an idea of mechanical necessity. If there is anything mystical or
even improbable in St. Hilaire's argument it does not appear on the
surface; for he did not assume that the response to the new environment was
always a favorable one or, as we say, an adaptation. He expressly stated
that _if_ the response was unfavorable the individual or the race died out.
He assumed that _sometimes_ the change might be favorable, i.e., that
certain species, entire groups, would respond in a direction favorable to
their existence in a new environment and these would come to inherit the
earth. In this sense he anticipated certain phases of the natural selection
theory of Darwin, but only in part; for his picture is not one of strife
within and without the species, but rather the escape of the species from
the old into a new world.

If then we recognize the intimate bond in chemical constitution of living
things and of the world in which they develop, what is there improbable in
St. Hilaire's hypothesis? Why, in a word is not more credit given to St.
Hilaire in modern evolutionary thought? The reasons are to be found, I
think, first, in that the evidence to which he appealed was meagre and
inconclusive; and, second, in that much of his special evidence does not
seem to us to be applicable. For example the monstrous forms that
development often assumes in a strange environment, and with which every
embryologist is only too familiar, rarely if ever furnish combinations, as
he supposed, that are capable of living. On the contrary, they lead rather
to the final catastrophe of the organism. And lastly, St. Hilaire's appeal
to sudden and great transformations, such as a crocodile's egg hatching
into a bird, has exposed his view to too easy ridicule.

But when all is said, St. Hilaire's conception of evolution contains
elements that form the background of our thinking to-day, for taken
broadly, the interaction between the organism and its environment was a
mechanistic conception of evolution even though the details of the theory
were inadequate to establish his contention.

In our own time the French metaphysician Bergson in his _Evolution
Creatrice_ has proposed in mystical form a thought that has at least a
superficial resemblance to St. Hilaire's conception. The response of living
things is no longer hit in one species and miss in another; it is precise,
exact; yet