As foon as the ftomach is filled, it’s capacity is enlarged, the
body is fhortened, Fig. 6, Plate XXIV . A, the arms are for the
mod part contracted, the polype hangs down without motion,
and appears to be in a kind o f ftupor, and very different from it’s
extended fhape ; but in proportion as the food is digefted, and it
has voided the excrementitious parts, the body lengthens, and
gradually recovers it’s form.
The tranfparency o f the polype permits us to fee diftinffly the
worm which has been fwallowed, Fig. 12, Plate XXIV. B, which
gradually lofes it’s form.' It is at firft macerated in the ftomach
o f the polype, and when the nutritious juices are feparated from
it, the remainder is difcharged by the mouth, Fig.'13. It is with
thefe as with other voracious animals, as they eat a great deal at
once, fo alfo they can faft for a long time. The hiftory of infeds
fumifhes many examples o f this kind.
One circumftance is obfervable, which probably contributes
much to the digeftion o f their food, namely, that the aliments are
continually pufhed back from one extremity to the other o f the
ftomach ; this motion may be eafily obferved with a microfcope,
in a polype which is not too full, and in which the food has been
already divided into little fragments. For thefe obfervations, it is
beft to feed the polype with fuch food as will give a lively-
coloured juice; as for example, thofe worms whofe inteftines are
filled with red fubftances: for by this means we fhall fee that
the nutritious juices are conveyed not only to the extremity o f
the body, but alfo into the arms, from whence it is probable that
each of the arms form alfo a kind o f gut, which communicates
with that o f the body. Some bits of a fmall black fnail, that is
frequently
frequently to be found in our ditches, was given to a polype.
The fubftance of this fkin was foon reduced into a pulp, confift-
ino- o f little black fragments ; on examining the polype with the
microfcope, thefe particles were perceived to be driven about the
ftomach, and to pafs from head to tail, and into their arms, even
where thefe were as fine as a thread; they were afterwards forced
into the ftomach, and from thence to the tail, from whence they
were again driven into the arms, and fo on.
The grains take their tinge from the food which nourilhes the
polypes -, thefe grains become red or black, if the polype be fed
with juices that are either red or black ; and they are more or lefs
tinged with thefe different colours, in proportion to the ftrength
and quantity of the nutritive juices. It is alfo obfervable, that
they lofe their colour if fed with aliments that are pot of the fame
colour with themfelves.
The polypes feed on the greater part o f thofe infefts that are to
be found in frefh water. They may be nourilhed with worms, the
larva of gnats; &c. they will alfo eat larger animals if they are
cut into fmall pieces, as fnails, large aquatic infefls, fmall fifh,
butchers meat, &c. Sometimes two polype's feize the fame
worm, and each begins to fwallow it’s own end, continuing fo to
do till their mouths meet, Fig. 8, Plate XX iV. A; in this pofition
they remain for fome time, at laft the worm breaks, and each has
it’s (hare; fometimes the combat does not end here, for each
continuing to difpute the prize, one of the polypes opens it’s
mouth advantageoully, and fwallows the other with its portion o f
the worm, fee Fig. 14, Plate XXIV. A ; this combat ends more
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