rs in the _Origin_, Ed. i. p. 427, vi. p. 583.

{144} _Air_ is evidently intended; in the MS. _water_ is written
twice.

Sec. VIII. UNITY [OR SIMILARITY] OF TYPE IN THE GREAT CLASSES.

Nothing more wonderful in Nat. Hist. than looking at the vast number of
organisms, recent and fossil, exposed to the most diverse conditions,
living in the most distant climes, and at immensely remote periods,
fitted to wholely different ends, yet to find large groups united by a
similar type of structure. When we for instance see bat, horse,
porpoise-fin, hand, all built on same structure{145}, having bones{146}
with same name, we see there is some deep bond of union between
them{147}, to illustrate this is the foundation and objects <?> <of>
what is called the Natural System; and which is foundation of
distinction <?> of true and adaptive characters{148}. Now this wonderful
fact of hand, hoof, wing, paddle and claw being the same, is at once
explicable on the principle of some parent-forms, which might either be
<illegible> or walking animals, becoming through infinite number of small
selections adapted to various conditions. We know that proportion,
size, shape of bones and their accompanying soft parts vary, and hence
constant selection would alter, to almost any purpose <?> the framework
of an organism, but yet would leave a general, even closest similarity in
it.

{145} Written between the lines occurs:--"extend to birds and other
classes."

{146} Written between the lines occurs:--"many bones merely
represented."

{147} In the _Origin_, Ed. i. p. 434, vi. p. 595, the term
_morphology_ is taken as including _unity of type_. The paddle of
the porpoise and the wing of the bat are there used as instances of
morphological resemblance.

{148} The sentence is difficult to decipher.

[We know the number of similar parts, as vertebrae and ribs can vary,
hence this also we might expect.] Also <if> the changes carried on to a
certain point, doubtless type will be lost, and this is case with
Plesiosaurus{149}. The unity of type in past and present ages of certain
great divisions thus undoubtedly receives the simplest explanation.

{149} In the _Origin_, Ed. i. p. 436, vi. p. 598, the author speaks
of the "general pattern" being obscured in the paddles of "extinct
gigantic sea-lizards."

There is another class of allied and almost identical facts, admitted by
t