24 UU. J. S. BOWERBANK ON HYALONEMA MIRABILE, [Jail, 10, 



fig. 3 representing a view of the interior of the distal portion of a 

 section through the middle of the valve at right angles to the cen- 

 tral axis of the oscular tube, by direct light; fig. 4 represents the 

 proximal diaphragm of the same specimen mounted in Canada bal- 

 sam. The action of these two valvular diaphragms appear to be 

 more or less independent of each other; and the radiating motive 

 fibres, comparatively few in number and very different in their 

 structure from those of the apical valve, are readily visible in their 

 natural condition when immersed in water or Canada balsam. This 

 is not the case with the motive organs of the more complicated apical 

 valve, which are deeply immersed in the substance of the apical 

 diaphragm, and which cannot be displayed until the internal disse- 

 pimental structures and the membrane above, which covers them, 

 are removed by the action of a solution of caustic potass for about 

 eight hours — Brandei-'s solution one part and distilled water three 

 parts being of about the inquired strength. When these impedi- 

 ments have been removed, the series of motive fibres present a very 

 interesting appearance. The whole consists of numerous spindle- 

 shaped fibres, one end of each being attached to the outer circum- 

 ference of the corrugated apical area, and the other end to the inner 

 circle of the sau-.e part, leaving a circular inner area of transparent 

 membranous structure, the middle of which has the natural orifice 

 of the osculuin in its centre, usually in a closed and puckered con- 

 dition. This parallel radial series of motive filaments, represented 

 in PI. IV. fig. .5, is doubtless not in its natural condition, the action 

 of the potass having probably increased the motive filaments to two 

 or three times their natural diameter ; so that, when in this state they 

 are forced by pressure or other means through the outer orifice of 

 the osculum, they may have been very readily mistaken for tenta- 

 ciila. The radial motive fibres in the specimen under consideration 

 appear to consist of a strong external membrane filled with dense 

 amber-coloured keratode, a]i]iarently the same substance as that 

 of which the corium is comjjosed. The inner membrane, covering 

 the under surface of this radial series of fibresj is apparently a much 

 more delicate tissue than th.at of the dissepiments of th.e valvular 

 structure beneath ; and the fragments disrupted by the action of the 

 ]>ctass are crowded v.ith minute elongated spiral cells ; but these 

 cells are not peculiar to this p;ortion of the membranous structures 

 of tlic corium, as I have found them aho in parts of (hat organ 

 which were not connected with the oscuLir tubes. Their i)Osition, 

 immersed deeply in the sarcodous membrane liuing the inner surface 

 of the apical valve, and closely covered by the distal end of the dis- 

 sepimental structures, and also comjdetely immersed in the sarcodous 

 membrane of the inner corium, would seem to indicate them to have 

 some other oftice in the economy of the animal than that of urti- 

 cating organs as suggested by Prof. Max Schultze. 



In the membrane forming the inner diaphragm, and in the paric- 

 tes of the tubular part of the osculum, there are frequently found 

 cylindro-cruciform and other s])icula of the same description as those 

 imbedded in the inner corium. These ))eculiar forms of spicula 



