138 THE OCEAN WORLD. 



firm, compact tissue. They are attached obliquely and alternately 

 upon a common axis, presenting an exterior curvature, a round 

 opening, furnished with a fine, muscular, and very contractile limb, 

 and arranged like the iris of the eye. Their power of resistance is 

 increased by certain horny hollow threads, which are in direct com- 

 munication with the cavity of the vertical axis, and have their origin 

 in a common circular canal. 



" The animal," says Vogt, " is enabled to guide itself in any 

 direction by means of the swimming apparatus or air-bags. These, 

 on opening, are filled with water, which is again ejected in the 

 contractile movement, for their movements may be compared to that 

 of the umbrella of the Medusae. It is the violent expulsion of this 

 liquid which enables the animal to advance diagonally through the 

 water, a kind of motion which is the consequence of its organisation ; 

 for where both rows of air-bags are working in the direction of the 

 axis of the stem, the organism will incline to the side which works 

 most, but always in such a manner that the aerial vesicle will be 

 borne forward." 



In its lower parts the stem expands, becomes flat, and winds itself 

 in a spiral. It is hollow, and encloses a transparent viscous liquid, 

 in which very small granules are observed, which appear to be the 

 result of digestion. To this are attached three different sorts of 

 appendages. We shall first address ourselves to the tentacles. 



These form a crown or bundle of vermiform appendages, of a 

 reddish colour, over an inch in length, and which are kept continually 

 in motion : these are formed of a glass-like cartilaginous substance ; 

 they are conical tubes, closed on all parts except at the point where 

 the tentacle is attached to the disc. Their cavity is filled with the 

 granulous liquid already mentioned. On the under surface of the 

 disc, and to the inside of these tentacles the polyps and fishing-lines 

 are attached. 



The anterior part of the polyp is formed of a glass-like substance, 

 which changes its form in the most varied and surprising manner. It 

 bears a roundish mouth at its summit. In its posterior part the 

 polyp presents a straight hollow stem, of reddish colour ; but near to 

 this red stem we find a thick tuft of cylindrical appendages, from the 

 middle of which spring the extensible and contractile filament which 

 Vogt calls the fishing-lines (fil pecheur), and of which he has given 

 the following very strange account : 



" Each of these appendages consists of an assemblage of cylindrical 

 tubes somewhat resembling and analogousto the filament of aConferva. 

 All these tubes are traversed by a continuous canal, which originates 



