ZOOFHYTA ASTEROIDA. 
167 
duction of theory than of observation, yet the opinion is in the 
main correct, and in correspondency with what had been long 
previously maintained by Ellis. In the spicula of Alcyonidse 
certainly, we can fi d no traces of organism, and they lie seem- 
ingly unconnected with the adjacent parts. The axis of Pen- 
natula is a solid bone formed of laminae laid over each other, 
softer and cartilaginous at each extremity where it seems to be 
O •/ 
organically connected with the soft surrounding flesh : it is evi- 
dently secreted, and deposited successively in layers, from the 
inner surface of a thin pellucid membrane which Bohadsch has 
described as investing it in the manner of a periosteum,* and 
probably is endowed with that low degree of vitality which pre- 
serves the horns, hairs and feathers of the higher animals in that 
elastic and fresh condition which they have only when in 
connection with living parts. The horny axis of Gorgonia, 
notwithstanding some observations of Ellis which apparently 
tend to a different conclusion,*!- is not more distinctly organized, 
and is doubtless formed in the same manner as the axis of Pen- 
natula, for it is also of a lamellated structure, and, according to 
Lamouroux, is invested with a similar periosteum. if A cross 
section of the stem or of a principal branch will show the layers 
to be disposed concentrically round a central medulla, the layers 
condensees, epurees par l’affinite, reunies, juxta-posees successivement, efc ont 
forme, par leur reunion, l’axe central et longitudinal dont il s’agit. Aussi cet 
axe est-il d’une substance continue, non poreuse.” — Anim. s. Vert. V. ii. p. 294* 
See also p. 78 — 80 ; and p. 311. 
* “ Totum os membrana tenuis, lutescens, pellucida cingit, atque in utroque 
extremo in ligamentum contorquetur, quod ex una parte in apice trunci pinnati, 
ex altera vero in apice trunci nudi inseritur.” — De Anim. mar. p. 104. See also 
Coral!, p. 214, 218, 224. 
f “ Proceeding thus far, I was led on to observe, wbat kind of communica- 
tion there was between the suckers (or polypes) and the bone of the animal ; 
for this end I examined several specimens, both dry, as well as those that were 
preserved in spirits, with good magnifying glasses, and could distinctly trace an 
infinite number of minute winding canals, that lead from the suckers through 
the flesh into those parallel longitudinal tubes, which closely surround the bone 
or solid part on all sides ; perhaps these may not improperly be called the peri- 
osteum ; for all along that side of those tubes by which they adhere to the bony 
part, I could discover the pores very plainly from whence the juices flow, that 
supply it with proper materials to answer this great end.” — Soland. Zooph. 69. 
} “ L’ecorce des Gorgoniees ne se lie pas immediatement a l’axe, elle en est 
sepai ee par une membrane d’une nature particuliere, si mince dans le genre 
Gorgonia, qu’il est tres-difficile de l’apercevoir ; elle est plus apparente dans les 
Plexaures et les Eunicees.” — Polyp. Corall, Flex. p. 391. 
