214 TOILERS IN THE SEA. 



of Pleurotoma which was dredged from 2,090 fathoms, 

 and "had a pair of well-developed eyes on short 

 footstalks; and a Fusus, from 1,207 fathoms, was 

 similarly provided. The presence of organs of sight," 

 he proceeds to say, "at these great depths leaves 

 little room for doubt that light must reach even these 

 abysses from some source. From many considera- 

 tions it can scarcely be sunlight, I have already 

 thrown out the suggestion that the whole of the light 

 beyond a certain depth might be due to phosphor- 

 escence, which is certainly very general, particularly 

 among the larvae and young of deep-sea animals, but 

 the question is one of extreme interest and difficulty, 

 and will require careful investigation." x 



As long since as 1853, M. de Quatrefages wrote a 

 memoir on the phosphorescence of the lower marine 

 .animals, which may even now be consulted with 

 interest, 2 in which he alludes to the fact that up to 

 that date four hundred and fifty authors had treated, 

 more or less fully, of the production of light by 

 organised beings. Even an abstract of this memoir, 

 which is in itself an abstract of antecedent observ- 

 ations, would scarcely be warranted here, and is 

 scarcely necessary, as it is available in an English 

 translation. 



1 "Depths of the Sea," p. 466. 



2 "Annals of Natural History," second series, vol. xii. 

 pp. 1 6, 1 80. 



