ACALEPH.fc 



0'9 



Physalus, (Jig- 24,) known to sailors by the name of the Por- 

 tuguese man-of-war, the swim- p igt 24. 

 in ing-bladder is single, and of 

 great proportionate size, so that 

 when full of air it is exceed- 

 ingly buoyant, and floats con- 

 spicuously upon the waves. The 

 top of this bladder bears a crest, 

 c, of a beautiful purple colour, 

 which, presenting a broad surface 

 to the wind, acts as a sail, by the 

 assistance of which the creature 

 scuds along with some rapidity. 

 The air-bladder is endowed with 

 a considerable power of contrac- 

 tion, and, when carefully exa- 

 mined, two orifices are observ- 

 able, one at each extremity, (a, &,) 

 through which, upon pressure, 

 the contained air readily escapes ; 

 a provision which enables the 

 creature to regulate its specific 

 gravity at pleasure, and, when alarmed, at once to lessen its buoy- 

 ancy by diminishing the capacity of its swimming-bladder, and 

 to sink into the waves. The nature of the air with which the 

 little voyager distends its float has not been accurately deter- 

 mined ; but it is undoubtedly a secretion furnished at pleasure 

 when at a considerable distance from the surface, although the 

 mode of its production is still unknown. 



Among the diversified forms of the Hydrostatic acalephse, few 

 are more elegant than one named by Peron Cuvieria cariso- 

 chroma (Jig. 27). In this beautiful medusa we find the floats 

 arranged like a string of pearls around the margin of its circular 

 body ; which, thus supported, spreads its long and delicate fila- 

 mentary tentacles to a considerable depth, in search of passing 

 food, as it swims upon the tranquil bosom of the ocean. 



(97.) Cirrigrada. The Cirrigrade acalephse form a very 

 remarkable family, peculiarly distinguished by the possession of 

 an internal solid support or skeleton secreted in the substance 

 of their soft and delicate bodies. In For pita (Jig. 25) this 

 consists of a flat plate of semicartilaginous texture, (2,) evi- 



