PYKOSOMA. 313 



mate of the watch came and called me to witness a 

 very unusual appearance in the water, which he, on 

 first seeing it, considered to be breakers. On arriving 

 upon deck, this was found to be a very broad and 

 extensive sheet of phosphorescence, extending in a 

 direction from east to west, as far as the eye could 

 reach. The luminosity was confined to the range of 

 animals in this shoal, for there was no similar light in 

 any other direction. I immediately cast the towing- 

 net over the stern of the ship, as we approached nearer 

 the luminous streak, to ascertain the cause of this 

 extraordinary and so limited phenomenon. The ship 

 soon cleaved through the brilliant mass, from which, 

 by the disturbance, strong flashes of light were emitted ; 

 and the shoal, judging from the time the vessel took 

 in passing through the mass, may have been a mile in 

 breadth. The passage of the vessel through them 

 increased the light around to a far stronger degree, 

 illuminating the ship. On taking in the towing-net, 

 it was found half filled with Pyrosoma (AtlanticumT), 

 which shone with a beautiful pale -greenish light ; and 

 there were also a few shell-fish in the net at the same 

 time. After the mass had been passed through, the 

 light was still seen astern, until it became invisible in 

 the distance ; and the whole of the ocean then became 

 hidden in the darkness as before this took place. The 



