Pknnatula. Z. ASTEROIDA. 177 



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 shep- 

 herd's crook. It consists, according to Sir E. Home, of phosphate 

 and carbonate of lime, making thus a near approach to the bone of 

 vertebrate animals. Lect. Comp. Anat. i. p. 59. 



The papillae on the back of the rachis, and between the pinnae, are 

 disposed in close rows, and do not differ from the polype cells except 

 in size. The latter are placed along the upper margin of a flattened 

 fin ; they are tubular, and have the aperture armed with eight 

 spinous points, which are moveable, and contract and expand at the 

 will of the animated inmates. These are fleshy, white, provided with 

 eight rather long retractile tentacula beautifully ciliated on the inner 

 aspect with two series of short processes, and strengthened moreover 

 with crystalline spicula, there being a row of these up the stalk, 

 and a series of lesser ones to the lateral cilise. The mouth, in the 

 centre of the tentacula, is somewhat angular, bounded by a white H- 

 garaent, a process from which encircles the base of each tentaculum, 

 which thus seems to issue from an apei tui'e. The ova lie betvi^een 

 the membranes of the pinnae ; they are globular, of a yellowish co- 

 lour, and by a little pressure can be made to pass through the mouth. 



Bohadsch says that the Pennatulae swim by means of their pinnae 

 which they use in the same manner that fishes do their fins. Ellis 

 says it " is an animal that swims freely about in the sea," " many of 

 them having a muscular motion as they swim along ;" and in ano- 

 tber place he tells us that these motions are effected by means of 

 the pinnules or feather-like fins, — " these are evidently designed by 

 nature to move the animal backward or forward in the sea, conse- 

 quently to do the office of fins." — Phil. Trans, abridg. xii. 42. Pal- 

 las adopted, with some reservation, J the opinion of Bohadsch ; but 

 Bosc, in an effort to be original, fancied that these remai'kable zoo- 

 phytes lay during the winter at the bottom, concealed among sea- 

 weed and in the crevices of rocks, while in summer they often swam 

 at the surface ! Cuvier tells us that they have the power of moving 

 by the contractions of the fleshy part of the polypidom, and also by 

 the combined action of its polypes ; and, to adopt the words of Dr 

 Grant, " a more singular and beautiful spectacle could scarcely be con- 

 ceived, than that of a deep purple Pen. phosphorea, with all its deli- 

 cate transparent polypi expanded and emitting their usual brilliant 

 phosphorescent light, sailing through the still and dark abyss by the 



• Misc. Zool. p. 177. 



