G. _A mass of the stem not so highly magnified shewing yᵉ. tubes
passing from stony to spongy._
_g._ _The same in its natural Size._
H. _The transverse section of the base shewing the holes in the ends of
the tubes._
I. _One of the radiated cells magnified, this is guarded by 8 pointed
valves, which close inward, when_
K. _the Polype draws in his head_ (_which is figur’d at_ K) _and opens
outward when it extends it._]
I now lay before you a piece of red coral (_See_ TAB. III. _Fig._ A.)
from the East Indies of a very singular kind, which I received from
your friend Abraham Hume, Esq. The stem and branches of this appear
evidently to the naked eye to consist of a combination of vermicular
tubes closely connected together: and, if we trace these little tubes
to their starry openings on the surface, _Fig._ B. we shall plainly
discover them to be the red testaceous coverings of certain marine
polypes, which have raised themselves thus upright, and disposed
themselves into this remarkable vegetable form.
In order to form some idea, how these masses are increased and extended
to the sizes we often meet with them, and where the same regularity of
shape is preferred in the large, that we find in the small; we think
it more than probable to suppose, that the species of polypes, that
compose this coral, breed as we find all other polypes do: and this
appears more evident to me, from what I have already discovered in
many kinds of corallines (_See Plate 38. of my Essay on Corallines_),
where the young polypes in some species are produced in the egg state,
while others fall in great numbers from their matrices, completely
formed, down to the roots of their parent corallines, either to begin
a new race of the same species near them, or to increase the trunk,
and extend the ramifications, of the plant-like figure which they just
descended from.
From observing this method in nature, we shall the easier account
for the progress of those generations of young testaceous polypes
of this coral; which appear to us succeeding each other, and raising
themselves up from the root or base, passing along the stem and
branches, and covering the whole anew with their shelly cases: and
in this their passage upwards we may observe, in the specimen before
us, how they have involved and incrusted the small lateral branches
of the former generation, so as almost to hide their appearance. From
hence we may trace them extending themselves to the extremities of
the upper branches, and there forming a new series of slender twigs,
proportionable to those which they had just covered, still keeping
order and exact symmetry in the whole structure.
The distinguishing character of this red coral, after we have
considered its fistulous texture, is the knotty joints, of which it
is composed: these appear more distinct, and are placed at a greater
distance, in the smaller branches than the large; and, as we descend to
the trunk, the traces of these inequalities but just appear.
From these protuberances, or knots, the lateral branches take their
rise; and as these and the leading branches grow up together, they
frequently inosculate at these joints, forming a kind of network, like
what we observe in many of those species of keratophyta, which are
called sea-fans.
The surface of this coral, when recent, is covered with a mealy friable
matter, of a yellow colour, not unlike that of the true red coral, but
much fuller of little raised starry cells. The figure of these cells is
owing to the radiated position of the claws of the polypes.
Upon removing this friable matter, we observe, that the polypes of
these cells have had a communication with a small hole or opening into
one of the tubes, that lie immediately under it.
This frequent intervention of the openings of the small tubes, or their
ramifications, between the sides of the larger ones, makes the latter
appear more irregular, and not so parallel, as in the true red coral;
where we find fewer stars; and, where those occur, we may observe it
always alters the direction of the tubes.
I must further remark to you, that many of the tubes of this coral
appear, thro’ a magnifying glass, full of small holes, like those I
have described in the keratophyton (_Plate_ 26. _Fig._ G. _p._ 62. _of
my Essay on Corallines_); and these holes will appear more distinctly
to you, when you examine the half tubes, or broken irregular ones, on
the stem and great branches of this coral.
Further, if you compare the transverse section, at the base of this
coral, with a section of a common Rattan cane, they will both appear
full of holes in the same regular order, and of nearly the same
diameter: whereas the tubes, on the surface of the stem of this coral,
look as irregular as so many holes pierced or eaten out by worms.
I hope by this time our ingenious botanical friends, whom we could
not persuade to part with these beautiful sea-productions from the
vegetable kingdom, are thoroughly convinced, that this mealy, friable,
or calcarious covering, full of starry cells, which we are sure to
find covering all the recent red corals and keratophyta, is not a mere
blight of insects, common to the sea vegetables as well as land ones,
which they have formerly insisted on; but that they will consider this
covering, for the future, as proper and necessary for the well-being of
these little animals, as they do at present hair and wool for beasts,
feathers and down for birds, and scales and slime for fishes.
This red coral is mentioned by Rumphius, in his _Herbarium Amboinense_,
Vol. vi. Tab. 85. p. 264, but, as the figure he has given, is not
sufficient to demonstrate its tubular texture and animal structure,
I have had it more accurately drawn; and those parts in particular
magnified, which may tend to illustrate the foregoing description.
He mentions, that it is in great esteem with them, on account of its
beautiful figure; but would be much more so, if it was not for the
great difficulty they find in preserving the smallest twigs from
falling off; which is the reason, I suppose, that the specimen is not
more complete.
Lastly, he tells us, that it is used by the inhabitants of the
Spice-islands as a principal ingredient in their medicines to expel
poison: as also, that they have it in great esteem on account of its
excellent diuretic quality.
Upon examining this coral in the microscope, I observed, that the
outside tubes of the stem were chiefly stony, but that the inward parts
were composed of as many divisions of spongy tubes, as there were of
stony ones.
This I find arises from the smaller ramifications, which being spongy
at the knobs, and stony in the spaces between them, are inclosed and
united together into one common mass during the growth of this coral;
so that both the soft and hard parts together make up the inside of its
trunk or stem. When we examine minutely the two parts, that compose
the branches, we find, that the knobs consist of little sponge-like
tubes interwoven together, as they appear magnified at _Fig._ D; and
the shank or part between the knobs is composed of stony tubes, that
are more erect (_See the piece magnified at_ E): these tubes appear to
be branched from the lateral holes at FF. The Fig. E likewise shews the
appearance of the tubes on the surface of the main stem.
The radiated openings in the little wart-like figures on the surface
of the branches are guarded by eight pointed valves, as magnified at
_Fig._ I.: these inclose the heads of the polype, one of which is
figured at K.
The stem of this specimen is so intirely divested of its yellow mealy
covering, that we may easily trace the manner in which the animals,
that compose it, have carried up their stony tubular cells, which lie
side by side along the surface. These tubes have still some marks
of sponginess at particular distances, which, as they come to join
together, form those irregular cross-lines, that surround the stem in
several places. _See Fig._ A.
In other specimens I have observed the principal stems covered over
with calcarious tubes, such as I have described in the Essay on
Corallines, _&c._ in that species of keratophyton called Venus’s Fan.
_Plate 26_.
The sponginess of the knobby joints occasions that excessive
brittleness in the lesser branches; which accounts for the difficulty,
which Rumphius mentions, of getting good specimens of this beautiful
coral.
I have lately seen a white pipy and stony coral with spongy knobs,
which is only a different species of this genus, in the very curious
cabinets of our friends Dr. John Fothergill, M. D. and Mr. Isaac
Romilly, F.R.S. specimens of which they have both lately received
from the East Indies. The examining of these has given me an
opportunity to be more particular in the description of this coral;
which seems to point out to us the great affinity there is between
corals, keratophyta, and sponges.