Origin of Species Variorum

→ fish, or, for I do not know which view is now generally held, a part of the auditory apparatus has been worked in as a complement to the swimbladder. 1859 1860 1861 1866

fish. 1869

fishes. 1872

→ seems to me to be no extreme difficulty in believing that natural selection 1861 1866

seems to me to be no great difficulty in believing that natural selection 1859 1860

is no reason to doubt that the swimbladder 1869 1872

→ converted a swimbladder into a 1859 1860 1861 1866

been converted into 1869 1872

→ On this view it may be inferred 1861 1866

I can, indeed, hardly doubt 1859 1860

According to this view it may be inferred 1869 1872

→ prototype, of which we know nothing, 1859 1860 1861 1866

and unknown prototype, which was 1869 1872

→ the 1859 1860 1861 1866

in the embryo the 1869

but in the embryo the 1872

→ embryo the slits 1866

slits 1859 1860 1861 1869 1872

→ marking 1866

marking in the embryo 1859 1860 1861

mark 1869 1872

→ in the same manner as, on the view entertained by some naturalists that 1859 1860 1861 1866

for instance, 1869

for instance, Landois has shown that 1872

→ branchiæ and dorsal scales of Annelids are homologous with the wings and wing-covers 1859 1860 1861 1866

branchiæ and dorsal scales of Annelids are believed to be homologous with the wings and wing-covers 1869

wings 1872

→ it is 1859 1860 1861 1866

and it is not 1869

are developed from the tracheæ; it is therefore highly 1872

→ organs which at a very ancient period 1859 1860 1861 1866

with our existing insects, organs, which at an ancient period 1869

in this great class organs which once 1872

namely,

namely

flotation, may be converted into one for a

wholly

widely

different purpose,

namely,

namely

respiration. The

swim-bladder

swimbladder

has, also, been worked in as an accessory to the auditory organs of certain →fish, or, for I do not know which view is now generally held, a part of the auditory apparatus has been worked in as a complement to the swimbladder. All physiologists admit that the

swim-bladder

swimbladder

is homologous, or "ideally

similar,"

similar"

in position and structure with the lungs of the higher vertebrate animals: hence there →seems to me to be no extreme difficulty in believing that natural selection has actually →converted a swimbladder into a

lungs,

lung,

an organ

organ

used exclusively for respiration.

→On this view it may be inferred that all vertebrate animals

with

having

true lungs

are

have

descended by ordinary generation from an ancient →prototype, of which we know nothing, furnished with a floating apparatus or

swim-bladder.

swimbladder.

We can thus, as I infer from

~~Professor~~

Professor

Owens

Owen's

interesting description of these parts, understand the strange fact that every particle of food and drink which we swallow has to pass over the orifice of the trachea, with some risk of falling into the lungs, notwithstanding the beautiful contrivance by which the glottis is closed. In the higher

Vertebrate

Vertebrata

the branchiæ have wholly

disappeared—

disappeared—but

disappeared—in

→the →embryo the slits on the sides of the neck and the loop-like course of the arteries still →marking their former position. But it is conceivable that the now utterly lost branchiæ might have been gradually worked in by natural selection for some

~~quite~~

quite

distinct purpose: →in the same manner as, on the view entertained by some naturalists that the →branchiæ and dorsal scales of Annelids are homologous with the wings and wing-covers of

insects

insects,

→it is

improbable

probable

that →organs which at a very ancient period served for

respiration,

respiration

have

actually been

been actually

converted into organs

for

flight.