his description of the remaining
monkeys. It comprises 250 pp., and is confined to details with which we
have no concern; but the last chapter--"De la Degeneration des
Animaux"--deserves much fuller quotation than my space will allow me to
make from it. The chapter is very long, comprising, as I have said, over
sixty quarto pages. It is impossible, therefore, for me to give more
than an outline of its contents.

_Causes or Means of the Transformation of Species._

The human race is declared to be the one most capable of modification,
all its different varieties being descended from a common stock, and
owing their more superficial differences to changes of climate, while
their profounder ones, such as woolly hair, flat noses, and thick lips,
are due to differences of diet, which again will vary with the nature of
the country inhabited by any race. Changes will be exceedingly gradual;
it will take centuries of unbroken habit to bring about modifications
which can be transmitted with certainty so as to eventuate in national
characteristics.[120] It is a pleasure to find that here, too, habit is
assigned as the main cause which underlies heredity.

Modification will be much prompter with animals. When compelled to
abandon their native land, they undergo such rapid and profound
modification, that at first sight they can hardly be recognized as the
same race, and cannot be detected in their disguise till after the most
careful inspection, and on grounds of analogy only. Domestication will
produce still more surprising results; the stigmata of their captivity,
the marks of their chains, can be seen upon all those animals which man
has enslaved; the older and more confirmed the servitude, the deeper
will be its scars, until at length it will be found impossible to
rehabilitate the creature and restore to it its lost attributes.

"Temperature of climate, quality of food, and the ills of slavery--here
are the three main causes of the alteration and degeneration of animals.
The consequences of each of these should be particularly considered, so
that by examining Nature as she is to-day we may thus perceive what she
was in her original condition."[121]

I have more than once admitted that there is a wide difference between
this opinion, which assigns modification to the direct influence of
climate, food, and other changed conditions of life, and that of Dr.
Erasmus Darwin, which assigns only an indirect effect to these, whil