hecus, in the habit of extending their membrane and even
their fingers to encompass a greater volume of air, so as to sustain
their bodies when they fly out into the air.

"By these habits, for so long a period contracted and preserved, the
bats have obtained not only lateral membranes, but also an
extraordinary elongation of the fingers of their fore feet (with the
exception of the thumb), between which are these very ample
membranes uniting them; so that these membranes of the hands become
continuous with those of the flanks, and with those which connect
the tail with the two hind feet, forming in these animals great
membranous wings with which they fly perfectly, as everybody knows.

"Such is then the power of habits, which have a singular influence
on the conformation of parts, and which give to the animals which
have for a long time contracted certain of them, faculties not found
in other animals.

"As regards the amphibious animals of which I have often spoken, it
gives me pleasure to communicate to my readers the following
reflections which have arisen from an examination of all the objects
which I have taken into consideration in my studies, and seen more
and more to be confirmed.

"I do not doubt but that the mammals have in reality originated from
them, and that they are the veritable cradle (_berceau_) of the
entire animal kingdom.

"Indeed, we see that the least perfect animals (and they are the
most numerous) live only in the water; hence it is probable, as I
have said (vol. ii., p. 85), that it is only in the water or in very
humid places that nature causes and still forms, under favorable
conditions, direct or spontaneous generations which have produced
the simplest animalcules and those from which have successively been
derived all the other animals.

"We know that the Infusoria, the polyps, and the Radiata only live
in the water; that the worms even only live some in the water and
others in very damp places.

"Moreover, regarding the worms, which seem to form an initial branch
of the animal scale, since it is evident that the Infusoria form
another branch, we may suppose that among those of them which are
wholly aquatic--namely, which do not live in the bodies of other
animals, such as the Gordius and many others still unknown--there
are doubtless a great many different aquatic forms; and that among
these aquatic worm