1867.] DR. J. S. BOWEK3AXK ON HYALONEMA MIRABILE. 25 



imbedded in sucli large quantities in tlie latter tissue miglit, by a 

 great stretch of iniagination, be thought to have been selected from 

 other extraneous matters around and- thus a]t])iopriated ; but this 

 solution of their presence in the valvular structure of the supjjosed 

 polvpe, deeply imbedded in its sarcodous niendjranes, is- certainly 

 inadmissible. In the valvular structures they are in a position in 

 A\hich secretion alone can account for their presence; and their ap- 

 pearance under such circumstances incontrovertibly connects them 

 with the corium on which the so-called polypes are based ; so, in like 

 manner, their abundant presence in the inner coriuin, and still more 

 profuse occurrence in the basal sponge, connects the corium and 

 basal sponge unmistakeably together. We have therefore, by means 

 of these peculiar and very striking forms of sj)icula, a sequence of 

 ])roof of a most conclusive character that the whole of the structures 

 present in the most perfect specimens of Ilyalonema are parts of 

 one and the same animal. 



Professors Brandt, Boeage, and INIax Schultze, in their respective 

 papers on Hyalonemu, believed that they had detected tentacula 

 within the heads of the oscular projections ; and the former two 

 have each figured what they regatwl as those organs with powers of 

 about 4 or o linear. The figures of the supposed tentacles of the 

 first and second named authors differ exceedingly ; and if each be 

 correct, their supposed ])oiypes cannot belong to the same genus. 

 The former author does not seem to have much faith in the reality 

 of what he depicts, as in the description of the figure 8. tab. 2, in 

 his work, he writes, " quoad tentacula expansa idealis." I have no 

 doubt that by soaking tlie oscular projections in a solution of caus- 

 tic potass, and by pressure or a little clever manipulation on the 

 softened and half-destroyed tissues of the valvular structure within 

 them, their motive fibres, which pass inward from the inner surfiice 

 towards the central diaphragm, may be loosened and withdrawn from 

 the apical orifice, and so disposed by pressure or otherwise as to 

 readily deceive an observer whose mind was previously occupied by 

 a foregone conclusion. 



I am well acquainted with the polype-cases of Zounihus coucldi in 

 the form of Di/sidea ■papiUosa, Johnston. They are stout open 

 tubes, composed of sand cemented together by animal matter, and 

 they have nothing within them like the elaborate keratose valvular 

 apparatus that we find in the distal ends of the oscular projections 

 in Ilyalonema: in fact their apices are jiermanently open ■\\hen the 

 polypes, tiieir former occupants, are destroyed. Nor have thev at 

 any time any appearance of tentacles upon them. Those orgaris at 

 all times appertain to the soft retractile polypes, and not to the poly- 

 pidoms that they inhabit. It has been suggested that Hyulonema 

 really consists of the basal spongcous mass, the spiral column of 

 spicula, and the inner sheath that surrounds it ; while the outer 

 sheath is a parasitical Zoanthoid Coral. But a careful examination 

 of the two sheaths surrounding the column affords such evidences 

 of the identity of their structures as to forcibly negative this sup- 

 position. 



