The Structure and Habits of Physalia. 365 



the side towards which, the inclination takes place. Besides this, 

 the creature has the power of raising up, into a nearly vertical 

 position at times, the free extremity of the pneumatophore. 

 Even when taken out of the water, and placed on any hard 

 surface, this portion of the creature continues to move, thus 

 indicating that the act is due to muscular contractibility of the 

 walls of the air-chamber, and not to the mere change of axis, 

 alluded to by M. de Quatrefages, which is due to the sudden 

 contraction of the tentacular appendages now about to be 

 described. 



On the inferior surface of Physalia there exists what appears, 

 at first sight, to be only a confused mass of tentacular and 

 suctorial organs. This mass consists of a duplicature of the 

 general substance of the body, termed the csenosarc by Pro- 

 fessor Huxley, from which three kinds of organs are given off, 

 namely, the " Polypites," the " Tentacles," and the " Hydro- 

 cysts." The first are variable in number and size, and, accord- 

 ing to the author just named, constitute the " principal organs 

 of alimentation." In outline they are somewhat pyriform or 

 flask-shaped, and during the life of the creature are in con- 

 tinual motion ; the broad open discoidal end being that which 

 is dependent, whilst the short pedunculate extremity is that 

 by which they are attached to, and communicate with, the cavity 

 of the csenosarc. Although these organs serve the purpose of 

 stomachs, they also possess the prehensile power imputed to 

 them, as may readily be seen in specimens placed in confine- 

 ment. The interior of the polypite is furnished with villous 

 projections, by means of which digestion and absorption are 

 said to be effected, and the nutritive products conveyed into 

 the general cavity of the body. The hydrocysts, which differ 

 in no aspect from the polypites, save in being completely closed 

 externally, have been regarded by Professor Huxley as " young 

 stomachs." 



The tentacles, in like manner with the polypites, are vari- 

 able in number and length, one being, however, generally much 

 longer than the rest. Each one is furnished at its point 

 of attachment with a jelly-bag-shaped sac, the mouth of 

 which communicates with the general cavity, and, along its 

 upper half, with that tentacle to the side of which it is adherent. 

 The tentacles in their contracted state are only a few inches in 

 length, whilst, in their extended condition, they often attain a 

 length of from four to six feet. They are formed of longi- 

 tudinal highly contractible fibres, each of which averages from 

 ■j-giyoth to 1T * Q th of an inch in diameter; the united fibres, when 

 extended, constituting a flattened band somewhat thicker on one 

 side than on the other, along which are attached at intervals, 

 crescentic masses composed almost wholly of thread capsules. 



