114 Dr Gmnt on the Structure and Nature of' Flusirce. 



tentacula, and 39,600,000 cilu». From the smallness of the cells of the F. fo- 

 /iacea, the immense number and size of the branches, and the cells being dis- 

 posed on both sides of the branches, the above calculations are often ten times 

 greater in that species. When the polypus is stretched out from its cell the 

 tentacula remain stiffly expanded in a bell-shaped form, their free extremi- 

 ties being all equally reflected outwards; and it is somewhat remarkable, that 

 when the polypi are torn, from their cells and exainined, quite dead^ in fresh 

 Arater, the tentacula remain in the same stiff expanded form. The tentacula 

 are exquisitely sensible, and we frequently observe them, either singly or all 

 at once, striking in their free extremities to the centre of the bell-shaped ca- 

 vity, when any minute floating body comes into contact with them. When 

 the polypus is expanded, there is a constant current of water towards its mouth, 

 produced by the rapid vibrations of the ciliae of the tentacula. The ciliae move 

 by far too rapidly to be followed by the quickest eye, aided by the most power- 

 ful microscope, and their motions are quite regular, ascending along one side 

 of the tentaculum, and descending along the other, like a current. These re- 

 gular motions appear more like some physical phenomenon than any move- 

 ments depending on volition, as I have just shown, that an ordinary sized 

 specimen of this animal can vibrate nearly 40,000,000 of ciliae at the same 

 instant with this incalculable velocity, — an exertion of volition altogether 

 inconceivable in an animal which exhibits no trace of a nervous system. 

 All the ciliae of a polypus appear to commence and cease their motions at the 

 same time. The bases of the tentacula are inserted into the outer margin of 

 abroad prominent lip surrounding the mouth of the polypus. When the 

 polypus is withdrawn into its cell, the tentacula form a close straight fascicu- 

 lus quite distinguishable, like every other part of the polypus, through the 

 transparent sides of the cell. The head of the polypus into which the tenta- 

 cula are inserted, is a little more dilated than the rest of the body, and 

 rounded ; and from the incessant revolution of particles observed within it, 

 this part seems to be ciliated internally, like the sides of the tentacula. The 

 head has the power of dilating itself by a sudden stroke, which is probably 

 produced by the sudden retraction of the prominent sides of the mouth, when 

 they have seized an animalcule. The tentacula and the head are of a white 

 colour, and the rest of the body is generally of a yellow, or sometimes of a blood- 

 red colour. We observe a fibrous capsule descending from the whole margin of 

 the aperture of the cell, to be inserted around the body of the polypus a little 

 below the head. This part is probably destined to aid the polypus in advancing 

 from the cell, or to protect the interior of the cell from foreign matter. From 

 the same part of the polypus numerous distinct fasciculi of soft fibres descend, 

 to be inserted into the base of the cell ; these appear destined to retract the 

 polypus into the cell. These fibres appear very much corrugated and inter- 

 woven at the bottom of the cell, when the polypus is entirely withdrawn into 

 its cavity. The body of the polypus is a lOng cylindrical fleshy tube of equal 

 thickness throughout, to near its extremity, where it tapers a little. The 

 body, after extending to the bottom of the cell, makes a curve backwards, and 

 again upwards to the centre of the cell, where the posterior extremity is bent 

 forward, and f o one side. From the part of the body which ascends to the 

 centre of the cellj about a sixth from the posterior end of the polypus, a 



