SEA-FAN MAKERS. 2 1 1 



the effect that electricity does not appear to 

 be the cause, but, " on the whole, it is most 

 probable that the animal secretes a spontaneously 

 inflammable substance. It may be a compound of 

 phosphorus, but it is not necessary to assume that 

 it is." 



There is a fascinating interest in the whole subject 

 of phosphorescence in marine animals, and at the 

 same time considerable mystery about its devplution. 

 How it is produced, what its immediate use, under 

 what conditions manifested, and whether always the 

 same in its source and nature, are all problems con- 

 stantly propounded, and never completely settled. 

 Like the light itself, these questions constantly elude 

 the grasp, and yet treatises have been written, and 

 suggestions offered, time after time, which only par- 

 tially, and very partially, meet the difficulty. Even 

 as recently as the date of the " Challenger Expedi- 

 tion " the subject has come again to the surface, as 

 the following allusions will indicate : 



While dredging in from 557 to 584 fathoms, Pro- 

 fessor Wyville Thomson says : " Many of the animals 

 were most brilliantly phosphorescent, and we were 

 afterwards even more struck by this phenomenon in 

 our Northern cruise. In some places nearly every- 

 thing brought up seemed to emit light, and the mud 

 itself was perfectly full of luminous specks. The 

 Alcyonarians, the brittle-stars, and some annelids 



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