24 LIVING LIGHTS. 



upon the polyps, a brilliant display of phosphorescence 

 followed. 



Doubtless nearly all the Alcyonarian ^^ corals are light- 

 givers, and of great importance in the illuminating economy 

 of the ocean. 



The Alcyonarians include the sea-pens (^PennatuUdce), 

 and the sea-fans and the red coral of commerce (^Gorgonias), 

 and may be briefly described as animals which, as a rule, 

 secrete a horny or calcareous stock, without the true divid- 

 ing septa that we see in the corals proper. 



The Alcyonarians dredged by the " Challenger " were 

 almost invariably brilliantly luminous, making the dredge 

 appear as if red-hot coals were being taken up. The light 

 of the deep-sea forms was similar to that of those dredged on 

 shallow banks, where the phosphorescence is remarkably 

 brilliant; so that we can imagine the wondrous spectacle 

 presented in these little known regions.^* 



The sea-fans and plumes, known scientifically as Gorgo- 

 nias, are extremely common upon the outer Florida reef, and 

 form the chief ornaments of these wonderful gardens of the 

 sea. We have drifted over them by day and night, peering 

 down into the depths, never wearjdng of the display. There 

 were two forms within diving distance on the reef, — one, a 

 rich yellow, reticulated fan ; and the 'other, a vivid lilac. On 

 the yellow we often found a parasitic shell of almost the exact 

 hue of the Gorgonia ; so like it, indeed, that it would not 

 have been noticed if the fan had not been closely examined, 

 — an interesting example of a protective resemblance. 



At night these waters present a wondrous appearance, 

 gleams of light flashing from every direction. Even the 

 sand at the bottom seemed to give out fitful coruscations ; 



