PEf T NATULA. 
Z. ASTEROIDA. 
177 
to a fine point. It seems intended to stiffen the polypidom, but it 
h es 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 ciliee. The mouth, in the 
centre of the tentacula, is somewhat angular, bounded by a white li- 
gament, a process from which encircles the base of each tentaculum, 
which thus seems to issue from an aperture. The ova lie between 
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- 
ther 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, ^ the opinion of Bohadsch ; but 
Bose, in an effort to be original, fancied that these remarkable 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. 
M 
