308 ZOOLOGY. 



as the tube within ; but should the body be much 

 handled, and kept long in water,, this orifice closes by 

 the contraction of a smooth membrane that surrounds 

 it like a sphincter water being at the same time re- 

 tained within the cavity of the body. This contraction 

 of the sphincter membrane is the only movement I have 

 seen the Pyrosome effect ; although it is said that the 

 creature has also the power of contracting and dilating 

 its entire body. 



THE SEA-NETTLE, OR PORTUGUESE MAN-OF-WAR. 



(Galtre of the French.) 

 (Phy sails Pelagica, Lamarck.) 



This is one of the most interesting and beautiful of 

 the hydrostatic acalepha. It obtains on the surface of 

 tropical seas generally, but more especially on the At- 

 lantic and Indian Oceans. Its habitat, as its spe- 

 cific name implies, is the open ocean, remote from 

 land ; though, being exposed to the influence of cur- 

 rents, examples are often found in great abundance on 

 the embayed waters of tropical coasts. 



The body of the Physalis consists of a horizontal py- 

 riform bladder, filled with air, semi-pellucid, about five 

 inches in length by three in height, and tapering to a 

 point at one extremity, while the opposite is rounded. 

 Its summit is occupied by a longitudinal ridge, or pro- 

 cumbent crest ; and nearly the entire length of its inferior 

 margin is furnished with a dense fringe of short ten- 

 tacles, from the midst of which there arise seven or 

 eight longer tentacula, or " cables." In one specimen 

 these cables measured more than seven feet in length. 

 They are each attached to the body by a bulbous base, 

 and have an oval plate, or sucker, at their free ex- 

 tremity. 



The colours displayed by this mollusc, when floating 



