Dr. Johnston's Catalogue of Zoophytes. 249 



P. Britannica, Soland. Zooph. 61. 



Penna marina, Sib. Scot. ii. lib. tert. 28; Petiv. Plant. Ital. t. 1, f. 5, 8, pessimae. 



Hab. On submarine banks, in about 30 fathoms water, common. 



Our fishermen call this polypidom the Cock's-comb, a name which is not unapt, but less 

 expressive of the general form than that of Sea-pen conferred by naturalists. It is from 

 two to three inches in length, and of a uniform purplish-red colour, except at the tip or 

 base of the stalk, where it is pale orange-yellow. The skin is thickish, very tough, and of 

 very anomalous structure, being composed of minute crystaline cylinders, densely arranged 

 in straight lines, and held together by a firm gelatinous matter or membrane. These cy- 

 linders are about six times their diameter in length, straight and even, closely compacted yet 

 distinct, and of a red colour, for the colour of the polypidom is derived from them, and they 

 are consequently less numerous where the purple is faint or defective. They are apparently 

 inorganic and calcareous, being dissolved, with effervescence, in the mineral acids.* Their 

 form and arrangement is the same in every part of the skin ; and the papillae on the back of 

 the rachis, as well as the polype cells are constructed of them, but none can be detected in 

 the gelatinous uncoloured substance found in the interior of the polypidom. 



The stalk is hollow in the centre, and contains a long slender bone, which is white, 

 smooth, square, and tapered at each extremity to a fine point. It seems intended to stiffen the 

 polypidom, but it does not extend the whole length of the stalk, for before it reaches either 

 end, the point is bound down and bent backwards like a shepherd's crook. It consists, ac- 

 cording to Sir E. Home, of phospate and carbonate of lime, making thus a near approach to 

 the bone of vertebrate animals. — Lect. on Comp. Anat. i. 59. 



The papillae on the back of the rachis are disposed in close rows, and do not differ from 

 the cells of the polypes except in size. The latter are placed along the upper side of a flat- 

 tened stalk, and are slightly arched : they are tubular, and have the apertures armed with 

 eight spinous points which are moveable, and contract and expand at the will of the ani- 

 mated inmates. These appear to be fleshy and white, and are provided with eight rather 

 long beautifully ciliated tentacula, protruded along the inner side of the spines just men- 

 tioned, so as to receive support and protection from them. 



The ova lie between the membranes of the pinnae or polype stalks at the base of the 

 cells: they are globular, and of a yellowish colour. 



Pennatula phosphorea floats at freedom in the bosom of the ocean, and can probably rise 

 or sink in it, to some extent, by alternately dilating or contracting the hollow stalk. It is, as its 

 name imports, a phosphorescent animal, but the fine blue light is emitted only under cer- 

 tain circumstances. I have never observed it to be phosphorescent when kept in sea water, 



* Dr. Coldstream, of Leith, on whose observations I place a greater reliance than on my own, 

 writes me thus — " The apicula of the Pennatula appear to me to be solid. I have examined them with 

 high powers, after having exposed them to a high temperature, and have not been able to see any evi- 

 dence of a cavity within; — whether viewed with reflected or transmitted light they seemed to be opake. 

 When connected with the body of the animal they certainly seem to be red, but a slight degree of heat 

 is sufficient to bleach them." 



