For
Some Time After The Rest Of The Animal Was Completely Dead
From The Effects Of Salt Water Or Any Other Cause, This Organ
Still Retained Its Vitality.
I found no less than twelve different species of terrestrial
Planariae in different parts of the southern hemisphere.
[3]
Some specimens which I obtained at Van Dieman's Land,
I kept alive for nearly two months, feeding them on rotten
wood. Having cut one of them transversely into two nearly
equal parts, in the course of a fortnight both had the shape
of perfect animals. I had, however, so divided the body,
that one of the halves contained both the inferior orifices,
and the other, in consequence, none. In the course of twenty-
five days from the operation, the more perfect half could
not have been distinguished from any other specimen. The
other had increased much in size; and towards its posterior
end, a clear space was formed in the parenchymatous mass,
in which a rudimentary cup-shaped mouth could clearly be
distinguished; on the under surface, however, no corresponding
slit was yet open. If the increased heat of the weather,
as we approached the equator, had not destroyed all the
individuals, there can be no doubt that this last step would
have completed its structure. Although so well-known an
experiment, it was interesting to watch the gradual production
of every essential organ, out of the simple extremity
of another animal. It is extremely difficult to preserve these
Planariae; as soon as the cessation of life allows the ordinary
laws of change to act, their entire bodies become soft
and fluid, with a rapidity which I have never seen equalled.
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