on which it so often rests.

"Likewise we perceive that the shore bird, which does not care to
swim, but which, however, is obliged (a _besoin_) to approach the
water to obtain its prey, will be continually in danger of sinking
in the mud, but wishing to act so that its body shall not fall into
the liquid, it will contract the habit of extending and lengthening
its feet. Hence it will result in the generations of these birds
which continue to live in this manner, that the individuals will
find themselves raised as if on stilts, on long naked feet; namely,
denuded of feathers up to and often above the thighs.

"I could here pass in review all the classes, all the orders, all
the genera and species of animals which exist, and make it apparent
that the conformation of individuals and of their parts, their
organs, their faculties, etc., is entirely the result of
circumstances to which the race of each species has been subjected
by nature.

"I could prove that it is not the form either of the body or of its
parts which gives rise to habits, to the mode of life of animals,
but, on the contrary, it is the habits, the mode of life, and all
the influential circumstances which have, with time, made up the
form of the body and of the parts of animals. With the new forms new
faculties have been acquired, and gradually nature has reached the
state in which we actually see her" (pp. 12-15).

He then points out the gradation which exists from the most simple
animal up to the most composite, since from the monad, which, so to
speak, is only an animated point, up to the mammals, and from them up to
man, there is evidently a shaded gradation in the structure of all the
animals. So also among the plants there is a graduated series from the
simplest, such as _Mucor viridescens_, up to the most complicated plant.
But he hastens to say that by this regular gradation in the complication
of the organization he does not mean to infer the existence of a linear
series, with regular intervals between the species and genera:

"Such a series does not exist; but I speak of a series almost
regularly graduated in the principal groups (_masses_) such as the
great families; series most assuredly existing, both among animals
and among plants, but which, as regards genera and especially
species, form in many places lateral ramifications, whose
extremities offer truly isolated points."

This is