n or a Goethe reached the
conviction that there are no limits.

LAMARCK VERSUS CUVIER

And even Goethe and Darwin had scarcely passed beyond that tentative
stage of conviction in which they held the thought of transmutation of
species as an ancillary belief not ready for full exposition. There was
one of their contemporaries, however, who, holding the same conception,
was moved to give it full explication. This was the friend and disciple
of Buffon, Jean Baptiste de Lamarck. Possessed of the spirit of a poet
and philosopher, this great Frenchman had also the widest range of
technical knowledge, covering the entire field of animate nature. The
first half of his long life was devoted chiefly to botany, in which he
attained high distinction. Then, just at the beginning of the nineteenth
century, he turned to zoology, in particular to the lower forms of
animal life. Studying these lowly organisms, existing and fossil, he
was more and more impressed with the gradations of form everywhere to be
seen; the linking of diverse families through intermediate ones; and
in particular with the predominance of low types of life in the earlier
geological strata. Called upon constantly to classify the various forms
of life in the course of his systematic writings, he found it more
and more difficult to draw sharp lines of demarcation, and at last the
suspicion long harbored grew into a settled conviction that there is
really no such thing as a species of organism in nature; that "species"
is a figment of the human imagination, whereas in nature there are only
individuals.

That certain sets of individuals are more like one another than like
other sets is of course patent, but this only means, said Lamarck, that
these similar groups have had comparatively recent common ancestors,
while dissimilar sets of beings are more remotely related in
consanguinity. But trace back the lines of descent far enough, and all
will culminate in one original stock. All forms of life whatsoever are
modified descendants of an original organism. From lowest to highest,
then, there is but one race, one species, just as all the multitudinous
branches and twigs from one root are but one tree. For purposes of
convenience of description, we may divide organisms into orders,
families, genera, species, just as we divide a tree into root, trunk,
branches, twigs, leaves; but in the one case, as in the other, the
division is arbitrary and artificial.

In Philosop