V 



TYROSOMATIDiE. 005 



Fam. PYROSOMATIDjE. 



Common body semi-cartilaginous, floating, cylindrical, 

 bearing externally numerous pointed tunicaries, hollow and 

 mamillated within, and open at one of its extremities only. 

 Tunicaries associated in a verticillate arrangement, having 

 two orifices, one at each extremity. 



The Pyrosomes inhabit the Mediterranean and the warmer 

 parts of the ocean, often occurring in incredible numbers. 

 The combined individuals form a hollow tube, open at one 

 extremity, which at night becomes vividly phosphorescent. 

 The tube is frequently of considerable dimensions, often 

 attaining a length of fourteen inches, and comprising 

 a multitude of delicate, transparent individuals, which by 

 their united efforts in ejecting the water from the cavity 

 of their mantles propel the cylinder in a slow and retro- 

 grade manner. When the calm surface of tropical seas is 

 densely studded with their myriads for several miles, the 

 Naturalist enjoys a splendid sight as the ship glides through 

 the pale green scintillating light. 



Genus PYROSOMA, Peron. 



Animal compound, the individuals forming a hollow 

 cylinder closed and rounded at one end and open at the 

 other, Each individual lies perpendicular to the axis of 

 the tube, and all are united together by a common, non- 

 contractile, cartilaginous basis, their inhalant apertures 

 opening externally, their exhalant orifices internally. 



Ex. P. giganteum, Savigny, pi. 136, fig. 2. Individual, 

 P. giganteum, fig. 2, a. 



VOL. it. 4 I 



