nized Lamarckism and Darwinism in these
words:

"We should, on account of the grand proofs just enumerated, have to
adopt Lamarck's Theory of Descent for the explanation of biological
phenomena, even if we did not possess Darwin's Theory of Selection.
The one is so completely and _directly proved_ by the other, and
established by mechanical causes, that there remains nothing to be
desired. The laws of _Inheritance_ and _Adaptation_ are universally
acknowledged physiological facts, the former traceable to
propagation, the latter to the _nutrition_ of organisms. On the
other hand, the _struggle for existence_ is a _biological_ fact,
which with mathematical necessity follows from the general
disproportion between the average number of organic individuals and
the numerical excess of their germs."[208]

A number of American naturalists at about the same date, as the result
of studies in different directions, unbiassed by a too firm belief in
the efficacy of natural selection, and relying on the inductive method
alone, worked away at the evidence in favor of the primary factors of
evolution along Lamarckian lines, though quite independently, for at
first neither Hyatt nor Cope had read Lamarck's writings.

In 1866 Professor A. Hyatt published the first of a series of classic
memoirs on the genetic relations of the fossil cephalopods. His labors,
so rich in results, have now been carried on for forty years, and are
supplemented by careful, prolonged work on the sponges, on the tertiary
shells of Steinheim, and on the land shells of the Hawaiian Islands.

His first paper was on the parallelism between the different stages of
life in the individual and those of the ammonites, carrying out
D'Orbigny's discovery of embryonic, youthful, adult, and old-age stages
in ammonites,[209] and showing that these forms are due to an
acceleration of growth in the mature forms, and a retardation in the
senile forms.

In a memoir on the "Biological Relations of the Jurassic
Ammonites,"[210] he assigns the causes of the progressive changes in
these forms, the origination of new genera, and the production of young,
mature, and senile forms to "the favorable nature of the physical
surroundings, primarily producing characteristic changes which become
perpetuated and increased by inheritance within the group."

The study of the modifications of the tertiary forms of Planorbis at
Steinheim, begun by Hilgendorf, led amon