SECT. m. PHYSALIID&. 1 1 1 



the canals of this Physophora are connected, and their 

 walls are lined with muscular fibres, either circular, 

 longitudinal, or both, which give a marvellous contrac- 

 tile and motive power. When the animal is suspended 

 from the surface of the sea by its float, every member is 

 in motion, especially the numerous tentacles, which are 

 perpetually in search of food, and are so extremely sen- 

 sitive that even a sudden motion of the water makes 

 them shrink under the red worm-like organs on the edge 

 of the disk. This animal is generally from one to three 

 inches long. 



All the preceding members of the physograde group 

 are really campanograde, for the action of the wind upon 

 the floats of the Physophoridae must be small, otherwise 

 they would not be furnished with so many swimming 

 cups. The Physaliidse and Yelellidse are the only two 

 orders that are truly physograde, for the wind is their 

 only locomotive power. 



The Physalia, or 'Spanish man-of-war' of sailors, is by 

 far the most formidable animal of the Acalephae tribe ; 

 its poisonous stings, which burn like fire, inflict instant 

 death on the inferior animals, and give painful wounds 

 to man himself. Its body, as it floats, is a long hori- 

 zontal double sac (fig. 121), which begins with a blunt 

 point, gradually enlarges, and becomes cylindrical about 

 the middle; then it somewhat suddenly widens in a 

 transverse or lateral direction. Along the upper surface 

 of the pointed half the membrane or wall of the sac is 

 raised into a transversely placed crest, which dies away 

 at the enlarged end. The greater part of the body is 

 smooth, but the under-surface of the transversely en- 

 larged end swells into lobes, from whence numerous 

 tentacles and other organs descend. 



Almost the whole of the body of the Physalia is filled 

 by an air-vessel, so that it floats on the surface of the 

 sea, and is wafted to and fro by the wind. The bladder 

 containing the air is enclosed in two membranes, the 



