s camels and sheep, which have undergone so total a transformation that
we are now ignorant from what species of wild animal they had their
origin. Add to these the great changes of shape and colour which we
daily see produced in smaller animals from our domestication of them, as
rabbits or pigeons, or from the difference of climates and even of
seasons; thus the sheep of warm climates are covered with hair instead
of wool; and the hares and partridges of the latitudes which are long
buried in snow become white during the winter months; add to these the
various changes produced in the forms of mankind by their early modes of
exertion, or by the diseases occasioned by their habits of life, both of
which become hereditary, and that through many generations. Those who
labour at the anvil, the oar, or the loom, as well as those who carry
sedan chairs or who have been educated to dance upon the rope, are
distinguishable by the shape of their limbs; and the diseases occasioned
by intoxication deform the countenance with leprous eruptions, or the
body with tumid viscera, or the joints with knots and distortions.

"Thirdly, when we enumerate the great changes produced in the species of
animals before their nativity, as, for example, when the offspring
reproduces the effects produced upon the parent by accident or
cultivation; or the changes produced by the mixture of species, as in
mules; or the changes produced probably by the exuberance of nourishment
supplied to the fetus, as in monstrous births with additional limbs;
many of these enormities of shape are propagated and continued as a
variety at least, if not as a new species of animal. I have seen a breed
of cats with an additional claw on every foot; of poultry also with an
additional claw, and with wings to their feet; and of others without
rumps. Mr. Buffon mentions a breed of dogs without tails which are
common at Rome and Naples--which he supposes to have been produced by a
custom long established of cutting their tails close off. There are many
kinds of pigeons admired for their peculiarities which are more or less
thus produced and propagated.[179]

. . . . . .

"When we consider all these changes of animal form and innumerable
others which may be collected from the books of natural history, we
cannot but be convinced that the fetus or embryon is formed by
apposition of new parts, and not by the distention of a primordial nest
of germs included one within anot