y been made by
C. H. Eigenmann (1895-96), W. J. Moenkhaus (1896), and H. C. Bumpus
(1896-98).

The discoveries of Owen, Gaudry, Huxley, Kowalevsky, Cope, Marsh,
Filhol, Osborn, Scott, Wortmann, and many others, abundantly prove that
the lines of vertebrate descent must have been the result of the action
of the primary factors of organic evolution, including the principles of
migration, isolation, and competition; the selective principle being
secondary and preservative rather than originative.

Important contributions to dynamic evolution or kinetogenesis are the
essays of Cope, Ryder, Dall, Osborn, Jackson, Scott, and Wortmann.

Ryder began in 1877 to publish a series of remarkably suggestive essays
on the "mechanical genesis," through strains, of the vertebrate limbs
and teeth, including the causes of the reduction of digits. In
discussing the origin of the great development of the incisor teeth of
rodents, he suggested that "the more severe strains to which they were
subjected by enforced or intelligently assumed changes of habit, were
the initiatory agents in causing them to assume their present forms,
such forms as were best adapted to resist the greatest strains without
breaking."[230]

He afterwards[231] claimed that the articulations of the cartilaginous
fin-rays of the trout (_Salmo fontinalis_) are due to the mechanical
strains experienced by the rays in use as motors of the body of the fish
in the water.

In the line of inquiry opened up by Cope and by Ryder are the essays of
Osborn[232] on the mechanical causes for the displacement of the
elements of the feet in the mammals, and the phylogeny of the teeth.
Also Professor W. B. Scott thus expresses the results of his
studies:[233]

"To sum up the results of our examination of certain series of
fossil mammals, one sees clearly that transformation, whether in the
way of the addition of new parts or the reduction of those already
present, acts just _as if_ the direct action of the environment and
the habits of the animal were the efficient cause of the change, and
any explanation which excludes the direct action of such agencies is
confronted by the difficulty of an immense number of the most
striking coincidences.... So far as I can see, the theory of
determinate variations and of use-inheritance is not antagonistic
but supplementary to natural selection, the latter theory attempting
no explanation of the _causes_ of variation. Nor