eir
attachment.

"The alteration which the cetaceans have undergone in their limbs,
owing to the influence of the medium in which they live and the
habits which they have there contracted, manifests itself also in
their fore limbs, which, entirely enveloped by the skin, no longer
show externally the fingers in which they end; so that they only
offer on each side a fin which contains concealed within it the
skeleton of a hand.

"Assuredly, the cetaceans being mammals, it entered into the plan of
their structure to have four limbs like the others, and
consequently a pelvis to sustain their hind legs. But here, as
elsewhere, that which is lacking in them is the result of atrophy
brought about, at the end of a long time, by the want of use of the
parts which were useless.

"If we consider that in the Phocae, where the pelvis still exists,
this pelvis is impoverished, narrowed, and with no projections on
the hips, we see that the lessened (_mediocre_) use of the hind feet
of these animals must be the cause, and that if this use should
entirely cease, the hind limbs and even the pelvis would in the end
disappear.

"The considerations which I have just presented may doubtless appear
as simple conjectures, because it is possible to establish them only
on direct and positive proofs. But if we pay any attention to the
observations which I have stated in this work, and if then we
examine carefully the animals which I have mentioned, as also the
result of their habits and their surroundings, we shall find that
these conjectures will acquire, after this examination, an eminent
probability.

"The following _tableau_[191] will facilitate the comprehension of
what I have just stated. It will be seen that, in my opinion, the
animal scale begins at least by two special branches, and that in
the course of its extent some branchlets (_rameaux_) would seem to
terminate in certain places.

"This series of animals beginning with two branches where are
situated the most imperfect, the first of these branches received
their existence only by direct or spontaneous generation.

"A strong reason prevents our knowing the changes successively
brought about which have produced the condition in which we observe
them; it is because we are never witnesses of these changes. Thus we
see the work when done, but never watching them during the process,
we are natural