i88 THE SEAS 



in countless numbers in the sea gives rise to that 

 general phosphorescence, or " burning of the sea" as it 

 was called by earlier observers, which has probably been 

 noticed by everyone who has had much experience of the 

 sea by night. Noctiluca is especially abundant in the 

 plankton during late summer and autumn and in this 

 season the prow of a boat cuts a silvery line through the 

 water — often of such brilliancy that even in the dead of 

 night a newspaper can be read by the light it casts. 

 Noctiluca itself is pinkish in colour and may be thrown 

 upon the shore in such numbers as to form a coloured layer 

 along the beach, the shore water resembling " thick tomato 

 soup." 



According to Murray and Hjort, the Norwegian fishermen 

 distinguish between " dead phosphorescence " and " fish 

 phosphorescence," the former resembling " the stars in a 

 clear sky, myriads of minute nearly invisible points emitting 

 a scintillating light, now increasing, now decreasing, in 

 intensity " and being produced by Noctiluca and similar 

 protozoa. The second type, the result of rushing move- 

 ments of large fish or squids which cause the phosphorescent 

 animals momentarily to glow, is more like a dull glow of 

 light which suddenly lights up and then dies out completely. 



Many jellyfish have the power of general luminescence 

 appearing as round balls of white fire in the sea. Those 

 seen and described by travellers in the warmer seas are 

 often of great size, and the late Professor Herdman describes 

 how, when at anchor on the pearl banks of the Gulf of 

 Manaar, "in an intensely dark night, I saw the black sea 

 around us in all directions lit up by an innumerable 

 assemblage of what looked like globes of fire, waxing and 

 waning in brightness, all simultaneously glowing and then 

 fading away into darkness, and after a few seconds light- 

 ing up once more. This periodic display continued for 



