in which he endeavoured to prove that all animals whatever are descended
from other species of animals. He attributed the change of species
chiefly to the effect of changes in the conditions of life--such as
climate, food, etc.--and especially to the desires and efforts of the
animals themselves to improve their condition, leading to a modification
of form or size in certain parts, owing to the well-known physiological
law that all organs are strengthened by constant use, while they are
weakened or even completely lost by disuse. The arguments of Lamarck did
not, however, satisfy naturalists, and though a few adopted the view
that closely allied species had descended from each other, the general
belief of the educated public was, that each species was a "special
creation" quite independent of all others; while the great body of
naturalists equally held, that the change from one species to another by
any known law or cause was impossible, and that the "origin of species"
was an unsolved and probably insoluble problem. The only other important
work dealing with the question was the celebrated _Vestiges of
Creation_, published anonymously, but now acknowledged to have been
written by the late Robert Chambers. In this work the action of general
laws was traced throughout the universe as a system of growth and
development, and it was argued that the various species of animals and
plants had been produced in orderly succession from each other by the
action of unknown laws of development aided by the action of external
conditions. Although this work had a considerable effect in influencing
public opinion as to the extreme improbability of the doctrine of the
independent "special creation" of each species, it had little effect
upon naturalists, because it made no attempt to grapple with the problem
in detail, or to show in any single case how the allied species of a
genus could have arisen, and have preserved their numerous slight and
apparently purposeless differences from each other. No clue whatever was
afforded to a law which should produce from any one species one or more