These four kinds only differ in form: they have the same qualities, are
made by the same kinds of worm, and what may be said of the one agrees
exactly with all the rest; for I made the same observations upon them
all.
They may be classed among the _spongiæ hyrcinæ_, so called by J.
Bauhin, because of the roughness of their fibres, by a metaphor, from
pieces covered with mud; or among those called by Pliny _tragos_, or
_aphysiæ_, being foul, and difficult to cleanse; and may take the name,
which Father Plumier has given them, drawn from their figure.
These four kinds of sponges are composed of hard, firm, dirty fibres,
sometimes brittle; separated one from another, having large hollows,
or cylindrical tubes, dispersed thro’ their substance. These tubes
are smooth within. The interstices of their fibres are filled with a
mucilaginous gluey matter, when the sponge is just taken out of the
sea. The mucilage is of a blackish colour, soon putrifies in the water,
or falls into dust when dried in the sun.
When a fresh sponge is squeezed, this mucilage comes out frothy, by
the mixture of the windings of its fibres: it always issues forth with
sand, or little parcels of shells crushed by the sea. These fibres,
which consist of the twisted doubles of the sponge, form as it were a
labyrinth filled with worms, which are easily crushed, and their juice
is confused with the mucilage; but having carefully torn the sponges,
and their gross fibres, I discovered the living worms, such as I shall
mention hereafter.
These species of sponge commonly grow upon sandy bottoms. At their
origins we perceive, as it were, a nodule of sand, or other matter,
almost petrified, round which the worms begin to work, and round which
they retire, as to their last seat or refuge; where I had the pleasure
of seeing them play, exercise themselves, and retire, by examining them
with the microscope; and I have even made my observations without its
assistance.
_A Description of the Worms which form the Sponges._
The worms I found in these kinds of sponges are about one-third of a
line thick, and two or three lines in length. They are so transparent,
that one may discern their _viscera_ thro’ their coverings and
substance: the blood may be seen to circulate, and all their parts to
act. They have a conic figure, with a small black head furnished with
two pincers: the other extremity is almost square, and much larger than
the head. Upon the back may be seen two white streaks or fillets, as if
they contained the chyle: these two canals are parallel to each other
from the head to the other extremity, where they come together. In the
middle, where the belly and _viscera_ ought to be placed, a blackish
matter is perceivable, which has a kind of circulation: sometimes
it fills all the body of the worm, sometimes it gathers towards the
head, or at the other end, and sometimes it follows the motion of the
animal. This vermicular motion or progression begins at the posterior
extremity, and ends at the head, which is pushed, and consequently
advances forward. I kept these worms alive out of the sponge, quite
detached from it, more than an hour, having examined them thoroughly
with a middling magnifier; for a great magnifier would be the grave of
the insect.
I was surprised, after having finished my observations, when I put them
near a piece of the fresh sponge, where the nests were moist, and from
which I had pulled them, to see them enter into them, and disappear,
being lost in the windings of the tubes. I thought to have found them
again; but it was a difficult task to search for them. I crushed them,
or they were themselves mashed in the tubes, which I pressed, and of
which I had consequently spoiled the texture; but I could not find
them; and this happened several times.
These worms have no particular lodge: they walk indifferently into
the tubular labyrinth. So that, without offence to Pliny and other
naturalists, I do not see, that it is in their power to dilate and
contract the bodies of the sponges; which always remain in the same
state of magnitude, without being any way sensible to the touch, or
any other motion of the sea, nor to any other accident whatsoever,
being an inanimate body; for the animal sensitive life, or whatever
you will have it, belongs only to the worms, that form these bodies,
and which are their dwelling-places; and which, by the slaver or juice
they deposit, make the sponge increase or grow, as bees, wasps, and
especially the wood-lice of America, increase their nests or cells.
These sponges, nests, or cells, are attached to some solid body in the
sea. Some kinds are fixed to rocks; others, as those I am speaking of,
are fastened to heaps of sand, or to pieces of petrified matter, and
even upon sandy bottoms; and the sea putting in motion the sand, and
the little parcels of broken shells, forces them into the holes of the
sponge: there the sand binds and mixes with mucilaginous juice, and
never is loosed from it but when the sponge is well dried, or with
the mucilage when putrified, or in powder; and yet some part will
remain, which it is very difficult to take out from the twisted canals,
especially in those sponges of the _tragos_ kind, so hard to cleanse.
In a word, the blood or humours, which the ancients have observed, is
no other than the mucilage or juice of the substance of these worms.
Dated at Guadaloupe, 1 March, 1757.
LXXIX. _Account of an Experiment, by which it appears, that Salt of
Steel does not enter the Lacteal Vessels; with Remarks. In a Letter to
the Rev._ Tho. Birch, _D. D. Secr. R. S. By_ Edward Wright, _M. D._
[Read Mar. 2, 1758.]