680 PHYSOGRADA. 



SECOND ORDER. PHYSOGRADA. (Gr. (pvv&co, plmsao, to inflate ; 

 Lat. gradior, to advance;) or SiPHONornoRA, (Gr. OKpuv, 

 siphon, a pipe or sucker, cpoytw, phoreo, to bear.) 



This order is composed of animals which are supported and 

 capable of moving in the water, by the possession of one or more 

 bladders, which they inflate with air at will. With reference to 

 this means of support, Cuvier called them Hydrostatic Acalephs. 

 When several air-bladders exist, instead of a single large one, 

 they are usually affixed to the same stalk, like currants upon 

 the stem, and rise out of the tentacular apparatus. 



The PORTUGUESE MAN-OF-WAR, Physalis, (Gr. water-bubble,) 

 pelagica, (Physalia pelagica. Linn.) This noted Acaleph (for 

 which see Chart,) has a very large air-vessel, beneath which the 

 digestive apparatus is arranged. The sac is surrounded by a 

 sort of crest or sail, which is usually elevated entirely above the 

 water, when the animal is floating at the surface. It has a 

 small orifice at each end, from which the air can be expelled 

 when the animal wishes to sink, and it is distended when it 

 wishes to rise. From the under side of the air-sac hangs a mass 

 of flask-shaped tentacular appendages terminated by suckers, and 

 sometimes hanging down like fish-lines, to an extent of fifteen or 

 sixteen feet. This creature possesses an active stinging power, 

 and is also very contractile, so that it is able to draw up its prey. 

 It would seem the short suckers are attached to the bodies of the 

 entrapped animals, and that the Physalis derives its nourishment 

 by imbibing their juices through the pores of its numerous cirri. 



The Physophora, (Gr. bladder-bearer,) Muzonema, has two 

 series of vesicles, and very numerous tentacles and filaments. 

 (See Chart.) 



The RHIZOPHYSA, (Gr. root-bladder,) has a very contractile 

 body with an aid-bladder at one extremity, and is provided 

 throughout its length with tentacular appendages covered or 

 mingled with filaments. (See Chart for figure of R. filiformis.} 



The Apolcmia Urania has an elongated worm-like body pos 

 sessing in the fore part two rows of numerous swimming organs, 

 and behind solid scaly organs, between which come forth tenta 

 cle-like cirri furnished with vermiform suckers. 



The Rliodophysa, (Gr. rhodon, a rose; phusa, a bladder,) Jieli- 

 anthus, (Gr. sun-flower,) has a short cylindrical and fleshy body, 

 swollen above into an air-bladder, and having below a number 

 of gelatinous rib-like formations with appended filaments. (See 

 Chart and PI. XVIII.fig.il.) 



