Part 12

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.

NASSA RETICULATA. Pl. VIII. fig. 2, a, b, c, d, e, f

A VERY active Mollusc, given here chiefly on account of the opportunity afforded by the birth of young fry in Mr. Lloyd’s tanks. The Nassa feeds on small animalcules, for which, in aquaria, it may be seen routing among the sand and stones, sometimes burying itself among them so as only to show its caudal tube moving along between them. A pair of Nassæ in Mr. Lloyd’s collection, deposited, on the 5th of April, about fifty capsules or bags of eggs upon the stems of weeds (fig. 2 b); each capsule contained about a hundred eggs. The capsules opened on the 16th of May, permitting the escape of rotiferous fry (fig. 2, c, d, e), not in the slightest degree resembling the parent, but presenting minute nautilus-shaped transparent shells. These shells rather hang on than cover the bodies, which have a pair of lobes, around which vibrate minute cilia in such a manner as to give them an appearance of rotatory motion. Under a lens they may be seen moving about very actively in various positions, but always with the look of being moved by rapidly turning wheels. We should have been glad to witness the next step towards assuming their ultimate form, but were disappointed, as the embryos died. Fig. 2 f is the tongue of a Nassa, from a photograph by Dr. Kingsley.

FOOTNOTES

{37} Sertularia operculata and Gemellaria lociculata; or any of the small Sertulariæ, compared with Crisiæ and Cellulariæ, are very good examples. For a fuller description of these, see Appendix explaining Plate I.

{67} If any inland reader wishes to see the action of this foot, in the bivalve Molluscs, let him look at the Common Pond-Mussel (Anodon Cygneus), which he will find in most stagnant waters, and see how he burrows with it in the mud, and how, when the water is drawn off, he walks solemnly into deeper water, leaving a furrow behind him.

{70} These shells are so common that I have not cared to figure them.

{72} Plate IX. Fig. 3, represents both parasites on the dead Turritella.

{74} A few words on him, and on sea-anemones in general, may be found in Appendix II. But full details, accompanied with beautiful plates, may be found in Mr. Gosse’s work on British sea-anemones and madrepores, which ought to be in every seaside library.

{90} Handbook to the Marine Aquarium of the Crystal Palace.

{111} An admirable paper on this extraordinary family may be found in the Zoological Society’s Proceedings for July 1858, by Messrs. S. P. Woodward and the late lamented Lucas Barrett. See also Quatrefages, I. 82, or Synapta Duvernæi.

{113} Thalassema Neptuni (Forbes’ British Star-Fishes, p. 259),

{116} The Londoner may see specimens of them at the Zoological Gardens and at the Crystal Palace; as also of the rare and beautiful Sabella, figured in the same plate; and of the Balanophyllia, or a closely-allied species, from the Mediterranean, mentioned in p. 109.

{118} A Naturalist’s Rambles on the Devonshire Coast, p. 110.

{121} Balanophyllia regia, Plate V. fig. 1.

{126a} Amphidotus cordatus.