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existence of a division of tlie genus Planaria, which inhabits
the dry land, interested me much. These animals are of so
simple a structure, that Cuvier has arranged them with the
intestinal worms, though never found within the bodies of
other animals. Numerous species inhabit both salt and
fresh water; but those to which I allude were found beneath
logs of rotten wood, even in the drier parts of the forest.
In general form they resemble little slugs, but are very much
narrower in proportion. I met with one specimen no less
than five inches long. The lower surface, by which they
crawl, is flat, the upper being convex : in this latter respect
the terrestrial species all differ from the depressed forms of
the aquatic. Their structure is very simple. Near the
middle of the under surface, there are two small transverse
slits, from the anterior one of which a funnel-shaped organ,
or cup, can be protruded. This seems to act as the
mouth. It is soft, highly irritable, and capable of various
movements ; when drawn within the body it is generally
folded up like the bud of a plant. From the central position
of the orifice, the animal has its mouth in the middle of what
would commonly be called its stomach! For some time
after the rest of the animal has become dead from the effects
of salt water, or other cause, this organ still retains its vitality.
The body is soft and parenchymatous ; in the central part a
transparent space, with lateral ramifications, appears to act as
a system of circulation. Minute, black, eye-like specks are
scattered round the margin of the crawling surface, and
more abundantly close to the anterior extremity, which is
constantly used as a feeler. In a marine species, I extracted
from the central parts of the body vast numbers of
little spherical eggs; they were .006 of an inch in diameter,
and contained a central opake mass or yolk.
The terrestrial Planariæ, of which I have found no less
than eight species, occur from within the tropic to lat. 47°
south, and are common to South America, New Zealand,
Van Diemen’s Land, and Mauritius. Some of the species
are longitudinally striped with several bands of gay colours.
At first sight there is a remarkable false analogy betw’cen
these animals and snails, although so widely separated
from each other in all essential points of organization.
I suppose these Planariæ feed on rotten wood, for they
are always found crawling on the under surface of old
decayed trees ; and some small specimens being kept wdtli
no other food, rapidly increased in size. Although gaily-
coloured little animals, they dislike, and are very sensitive
to the light. Some specimens W’hich I obtained at
Van Diemen’s Land, I kept alive for nearly two months.
Having cut one of them transversely into two nearly equal
parts, m 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,
m which a rudimentary cup-shaped organ 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 Planariæ; immediately the cessation of life
aUows the ordinary laws of change to act, their entire
bodies become soft and fluid, with a rapidity which I have
never seen equalled. A method of preservation that I found
answered pretty well, was to dry the whole animal rapidiv
on a thin plate of mica, for the body thus becomes
transparent, and allows the internal structure to be seen,
first visited the forest in which these Planariæ were
I (fit