Narrative ov Bahama Expedition. 55 



ripple luminous. The vessel seemed to be bathed in ghostly 

 flame, as the millions of light-emitting animals gave each its 

 quota to the display. Nothing is better calculated to impress 

 one with the intinite number of living things to which Old 

 Ocean yields home and livelihood. We found that here, as in 

 the Gulf Stream, the little thimble-shaped Lincrgxs merciirms 

 was the cause of the greater part of the luminosity, although 

 ctenophores. pelagic Crustacea and Koctihtca added greatly 

 to the general effect, while more than once we saw the ghostl}' 

 trail of what we took to be Pyrosouia, although the animal 

 was not secured. 



The most brilliant phosphorescence seen during the voyage 

 of the '• Challenger " was encountered in the Guinea current, 

 not far from the Cape Verde Islands. Sir Wyville Thomson 

 sa3's.^ •• The wake of the ship was an avenue of intense bright- 

 ness. It was easy to read the smallest print, sitting at the 

 after port in the cabin." We saw no such brilliant effects as 

 this, but the writer has seen in the Gulf of Nicoya, on the 

 Pacific coast of Costa Rica, an equall}^ intense displa}-, dis- 

 tinctly lighting up the decks of a large steamer, and enabling 

 one to read at intervals the print of an ordinary newspaper. 



The purpose of this phosphorescence is somewhat difficult 

 to explain on the supposition that it must be of use to its pos- 

 sessors. Verrill regards it as protective, at least among the 

 gorgonians where, he suggests, the light may act as a warn- 

 ing to predatory iishes. Doubtless it may be explained in 

 many instances as an aid to the sexes in finding each other at 

 night or in deep water. Again, it probably assists carnivo- 

 rous fishes and Crustacea in discovering and capturing their 

 prey in deep water. 



Until the physiology of the light-emitting organs in various 

 animals is better understood, it will perhaps be impossible .to 

 do more than conjecture regarding their true significance. 



On Tuesday, May i6th, no dredging w^as done, the wind 

 allowing us to make some headwav on our course. Most of 



1 X'uyage of the "Challenger," Atlantic. \'c)hinie 2. Page 71. 



