312 THE OCEAN WORLD. 



is also found in the same sea. It is a long bluish cylinder shape 

 bristling with bracts, at the base of each of which is the abode of a 

 polyp, a citizen of this moving republic, which is attached to its 

 colleagues by means of its gelatinous envelope, an alliance imposed 

 by inexorable Nature. 



Another species, P. atlanticum, was discovered by Peron and 

 Lesueur in the equatorial seas. 



These curious Tunicates grow in such a manner as to constitute a 

 long fine cylindrical tube, closed at one end and open at the other. By 

 the contraction and dilatation of the mass of beings, this great cylinder 

 swims slowly through the open sea, lighting up the ocean with its 

 phosphorescent light, shining through the water like a glowing fire. 

 Mr. Bennett thus describes the phenomenon presented by these 

 creatures. " On the 8th of June, being then in lat. 30"^ S. and 27'' 

 5' W. long., having fine weather and a fresh south-easterly trade-wind, 

 and the thermometer ranging from 78° to 84°, late at night the mate 

 of the watch called me to witness a very unusual appearance in the 

 water. This was a broad and extensive sheet of phosphorescence 

 extending from east to west as far as the eye could reach. I 

 immediately cast the towing net over the stern of the ship, which 

 soon cleaved through the brilliant mass, the disturbance causing 

 strong flashes of light to be emitted, and the shoal, judging from the 

 time the vessel took in passing through the mass, may have been a 

 mile in breadth. On taking in the towing-net, it was found half filled 

 with Pyrosoma atlaniiciim, which shone with a beautiful pale greenish 

 light. After the mass had been passed through by the ship, the 

 light was still seen astern, until it had became invisible in the 

 distance, and the ocean became hidden in the darkness as before 

 this took place. 



" The second occasion of my meeting these creatures was in a 

 high latitude, and during the winter season. It was on the 19th ot 

 August, the weather dark and gloomy, with light breezes from north- 

 north-east, in lat. 40° 30' S., and 138'' 3' E. long., at the western en- 

 trance to Bass's Straits, and about eight o'clock p.m., when the ship's 

 wake was perceived to be luminous, while scintillations of the same 

 light were abundant all round. To ascertain the cause, I threw the 

 towing-net overboard, and in twenty minutes succeeded in capturing 

 several Pyrosoma, which gave out their usual pale green light ; and 

 it was, no doubt, detached groups of these animals which were the 

 occasion of the light in question. The beautiful light given out by 

 these molluscans soon ceased to be seen ; but by moving them about 

 it could be reproduced for some length of time after. The luminosity 



