The cells are alternate on the stem, and are curiously armed with long
whip-like cilia or spines. On the back of some of the cells is a very
strange appendage, the use of which is not with certainty ascertained.
It is a minute body, slightly resembling a vulture’s head, with a movable
lower beak. The whole head keeps up a nodding motion, and the movable
beak occasionally opens widely, and then suddenly snaps to with a jerk.
It has been seen to hold an animalcule between its jaws till the latter
has died, but it has no power to communicate the prey to the polype in
its cell or to swallow and digest it on its own account. It is certainly
not an independent parasite, as has been supposed, and yet its purpose in
the animal economy is a mystery. Mr. Gosse conjectures that its use may
be, by holding animalcules till they die and decay, to attract by their
putrescence crowds of other animalcules, which may thus be drawn within
the influence of the polype’s ciliated tentacles. Fig. 7 B shows the
form of one of these “birds’ heads,” and fig. 7 C, its position on the
cell.
FLUSTRA LINEATA. _Pl._ I. _fig._ 1.
In Flustræ, the cells are placed side by side on an expanded membrane.
Fig. 1 represents the general appearance of a species which at least
resembles F. lineata as figured in Johnston’s work. It is spread upon a
Fucus. Fig. A is an enlarged view of the cells.
FLUSTRA FOLIACEA. _Pl._ I. _fig._ 2.
We figure a frond or two of the common species, which has cells on both
sides. It is rarely that the polypes can be seen in a state of
expansion.
SERIALARIA LENDIGERA. _Pl._ I. _fig._ 10.
NOTAMIA BURSARIA. _Pl._ I. _fig._ 11.
The “tobacco-pipe”“ appendages, fig. 11 B, are of unknown use: they are
probably analogous to the birds’ heads in the Cellularæ.
PLATE V.
CORALS AND SEA ANEMONES.
CARYOPHYLLÆA SMITHII. _Pl._ V. _fig._ 2. _Pl._ VI. _fig._ 3.
THE connection between Brainstones, Mushroom Corals, and other Madrepores
abounding on Polynesian reefs, and the “Sea Anemones,” which have lately
become so familiar to us all, can be seen by comparing our comparatively
insignificant C. Smithii with our commonest species of Actinia and
Sagartia. The former is a beautiful object when the fleshy part and
tentacles are wholly or partially expanded. Like Actinia, it has a
membranous covering, a simple sac-like stomach, a central mouth, a disk
surrounded by contractile and adhesive tentacles. Unlike Actinia, it is
fixed to submarine bodies, to which it is glued in very early life, and
cannot change its place. Unlike Actinia, its body is supported by a
stony skeleton of calcareous plates arranged edgewise so as to radiate
from the centre. But as we find some Molluscs furnished with a shell,
and others even of the same character and habits without one, so we find
that in spite of this seemingly important difference, the animals are
very similar in their nature. Since the introduction of glass tanks we
have opportunities of seeing anemones crawling up the sides, so as to
exhibit their entire basal disk, and then we may observe lightly coloured
lines of a less transparent substance than the interstices, radiating
from the margin to the centre, some short, others reaching the entire
distance, and arranged in exactly the same manner as the plates of
Caryophyllæa. These are doubtless flexible walls of compartments
dividing the fleshy parts of the softer animals, and corresponding with
the septa of the coral. Fig. 2 _a_ represents a section of the latter,
to be compared with the basal disk of Sagartia.
SAGARTIA ANGUICOMA. _Pl._ V. _fig._ 3, _a_, _b_.
This genus has been separated from Actinia on account of its habit of
throwing out threads when irritated. Although my specimens often assumed
the form represented in fig. 3, Mr. Lloyd informs me that it must have
arisen from unhealthiness of condition, its usual habit being to contract
into a more flattened form. When fully expanded, its transparent and
lengthened tentacles present a beautiful appearance. Fig. 3 _a_, showing
a basal disk, is given for the purpose already described.
BALANOPHYLLÆA REGIA. _Pl._ V. _fig._ 1.
Another species of British madrepore, found by Mr. Gosse at Ilfracombe,
and by Mr. Kingsley at Lundy Island. It is smaller than O. Smithii, of a
very bright colour, and always covers the upper part of its bony
skeleton, in which the plates are differently arranged from those of the
smaller species. Fig. 1 shows the tentacles expanded in an unusual
degree; 1 _a_, animal contracted; 1 _b_, the coral; 1 _c_, a tentacle
enlarged.
PLATE VI.
CORALS AND SEA ANEMONES.
ACTINIA MESEMBRYANTHEMUM. _Pl._ VI. _fig._ 1 _a_.
THIS common species is more frequently met with than many others, because
it prefers shallow water, and often lives high up among rocks which are
only covered by the sea at very high tide; so that the creature can, if
it will, spend but a short portion of its time immersed. When uncovered
by the tide, it gathers up its leathery tunic, and presents the
appearance of fig. 1 _a_. When under water it may often be seen
expanding its flower-like disk and moving its feelers in search of food.
These feelers have a certain power of adhesion, and any not too vigorous
animals which they touch are easily drawn towards the centre and
swallowed. Around the margin of the tunic are seen peeping out between
the tentacles certain bright blue globules looking very like eyes, but
whose purpose is not exactly ascertained. Fig. 1 represents the disk
only partially expanded.
BUNODES CRASSICORNIS. _Pl._ VI. _fig._ 2.
This genus of Actinioid zoophytes is distinguished from Actinia proper by
the tubercles or warts which stud the outer covering of the animal. In
B. gemmacea these warts are arranged symmetrically, so as to give a
peculiarly jewelled appearance to the body. Being of a large size, the
tentacles of B. crassicornis exhibit in great perfection the adhesive
powers produced by the nettling threads which proceed from them.
CARYOPHYLLÆA SMITHII. _Pl._ VI. _fig._ 3.
This figure is to show a whiter variety, with the flesh and tentacles
fully expanded.
PLATE VIII.
MOLLUSCA.