Origin of Species Variorum

→ subsequently modified, 1869 1872

modified since their arrival, could 1859 1860 1861 1866

→ specify one such difficult case. 1869

here give a single instance of one of the cases of difficulty. 1859 1860 1861 1866

specify one difficult case. 1872

→ elsewhere,— striking instances of which have been given by Dr. A. A. Gould in relation to the Pacific. 1869 1872

elsewhere. 1859 1860 1861 1866

↑ 1 blocks not present in 1869 1872; present in 1859 1860 1861 1866

Dr. Aug. A. Gould has given several interesting cases in regard to the land-shells of the islands of the Pacific.

→ be, according to our view, 1869

be, on my view, 1859 1860 1861 1866

be 1872

→ sometimes 1869 1872

occasionally crawl on and 1859 1860 1861 1866

→ shell, 1869 1872

of these shells was 1859 1860 1861 1866

→ having been thus treated and 1869 1872

it had 1859 1860 1861 1866

→ of average swiftness, 1869 1872

running at an average rate, 1866

I do not deny that there are many and

grave

serious

difficulties in understanding how

several

many

of the inhabitants of the more remote islands, whether still retaining the same specific form or →subsequently modified, have reached their present homes. But the probability of

many

other

....

islands having

once existed

existed

as halting-places, of which not a wreck now remains, must not be

over- looked.

over-looked.

overlooked.

I will →specify one such difficult case. Almost all oceanic islands, even the most isolated and smallest, are inhabited by land-shells, generally by endemic species, but sometimes by species found →elsewhere,— striking instances of which have been given by Dr. A. A. Gould in relation to the Pacific. ↑ Now it is notorious that land-shells are

very

....

easily killed by

salt;

sea-water;

their eggs, at least such as I have tried, sink in

sea-water

sea-water,

and are

killed

killed.

....

it.

....

Yet there must →be, according to our view, some unknown, but

highly

occasionally

efficient means for their transportal. Would the just-hatched young →sometimes adhere to the feet of birds roosting on the ground, and thus get transported? It occurred to me that land-shells, when hybernating and having a membranous diaphragm over the mouth of the shell, might be floated in chinks of drifted timber across moderately wide arms of the sea. And I

find

found

that several species

did

....

in this state

withstand

withstood

uninjured an immersion in sea-water during seven days: one →shell, the Helix pomatia,

and

....

after →having been thus treated and again

hybernated

hybernating

was

put

it in

it into

into

sea-water for twenty days, and

....

perfectly recovered. During this length of time

the shell

might have been carried by a marine

current,

current

→of average swiftness, to a distance of 660 geographical miles. As this Helix has a thick calcareous operculum, I removed it, and when it had formed a new membranous one, I again immersed it for fourteen days in sea-water, and

again it

recovered and crawled away. Baron Aucapitaine has

since

recently

tried similar

experiments:

experi- ments: