310 



NATURAL HISTORY. 



TUBIPORA MUSICA. 



other, and separated by a kind of semi-tubular and cellular tissue, which forms layers of considerable 

 extent. Usually the number of tubes is small at the base of a mass, and it increases at each layer of 

 the cellular tissue, so that it is very great at the surface of a large piece. Each tube is made up of a 

 great number of sclerites, nearly united together, so that their original shape cannot be made out, 

 and it is hollow within, and more or less cylindrical. But there are funnel-shaped projections inside, 

 and also incomplete horizontal tabulae. There are no septa. The tubes are separate, slightly porose, 

 and the new ones spring from the horizontal layers, whose cavities communicate with the larger tubes. 

 The polype fills the upper part of the tube, and its outer derm passes over the edge, or rather is 

 continuous with it, and the sclerites are developed in its midst. There are eight tentacles, with from 

 fifteen to seventeen pinnae on either side of each, and there are spicules within. The mouth has a 

 slightly raised lip. When the polype is alarmed, the tentacles close, and then the whole is with- 

 drawn into the tube. The lower part of the tube, above the uppermost tabula, is occupied by the 

 gastric cavity, separated above from the stomach by a delicate tissue. The ovaries are in the lower 

 cavity, and the mesenteries, eight in number, are like thin slender cords. 



The genus Tubipora forms a sub-family of the Alcyonidae, and there are several species of 



it. Probably it is of great antiquity, for there are things like 

 it in the Devonian rocks. 



The Alcyoninae are fleshy and soft, and increase by ova, 

 and also in. mass by a process of budding from the sides of 

 the polypes. The buds are enclosed in a very strongly- 

 developed coenosarc, and the mass may be simple, lobed, or 

 branched. There are two divisions of the sub-family. In 

 the armed or spiculate one, the tissue of the body is thin 

 and soft deeply, but the outer derm is almost consolidated 

 or very leathery, on account of the number of large boat- 

 shaped spiculaj. These resemble those commonly found in 

 L Tunes magnified and containing polype. 2 Tentacles of the Alcyonaria at the base of the tentacles, but which are 



Ttilnpora polype. 3. Polype magnified. * 



small in that position. The extremities of the spicules 



project at the surface, and give an echinulate appearance to the individual. In the genus Nephthya 

 the derm is a leathery skin, bristling with spicules, and it forms branching lobes ending in projecting 

 tubercles in which are the polypes. The only known species is from the Red Sea. In the genus 

 Spoggodes the animal is membranous and flexible, and the polypes are incompletely retractile within 

 the tissue which contains the spicules. An almost cylindrical tube of leathery skin with spiculiferous 

 walls contains the highly retractile polypes of the genus Paralcyonium of the Algerian seas, and this is 

 the nearest ally to the Tubipores. No less than twelve genera belong to the next division of naked 

 Alcyonians. These have a semi-cartilaginous consistence, and merit the term fleshy, but the density is 

 due to the presence of a multitude of microscopic nodular sclerites. The surface is granular and very 

 spinulose. The genera may be grouped according to the contractility of the polypes ; and in the 

 genus Alcyonium, which is lobed-shaped or finger-shaped, the contractility is complete. The polypes 

 retreat within a dense coanosarc ; they increase by budding. One of the species* has a singular hand- 

 shape, and is called Dead Man's Fingers on the English coasts. The polypes are large, very numerous, 

 and occupy the greater part of the surface, and the colour may be white, or grey, or orange. They 

 are fixed on to stones and shells, and the ugly mass of slimy-looking substance if placed in pure 

 sea-water gradually sends forth its beautiful polypes. The genus Ammothea is a branching form, 

 with spicules on the branches, and it probably should be placed with the other division. Its 

 polypes are semi-retractile. 



The polypes of the last genus to be mentioned, Xenia, from the Red Sea and Fijis, are 

 non-retractile, and are on a fasciculate and fleshy stem. 



Amongst the genera of the sub-family, the Cornularinae, are some simple or isolated forms, or 

 they may be united by a kind of prolonged base or stolon, out of which they have been formed 

 by budding. 



The simple kinds have a tubular shape, and the polype is retractile, and they belong to the 



* Ah'uoinum diyitalum. 



