ZOOPHYTA 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 Alcyonidae 

 certainly, we can find 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 extremitv where it seems to be 

 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 Gorgon ia, 

 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. % 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 



coiidensees, epurees par I'affinite, reunies, juxta-posees successivement, et ont 

 forme, par leur reunion, I'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 in.seritur." — De Anim. mar. p. 104. See also 

 Corall. p. 214,218,224. 



f " Proceeding thus far, I was led on to observe, what 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 I'axe, elle en est 

 separee par une membrane d'une nature particuliere, si mince dans Ic genre 

 Horgonia, qu'il est tres-difficilc de I'apcrrevoir ; elle est plus apparentc dans les 

 Plexaures et les Eunicees." — Polyp Corall. Flex. p. 391. 



