184 M. de Quatrefages on the Phosphorescence of 



I have many times sought for the cause of the bright sparks 

 which I saw shining and then vanishing in darkness. In each 

 case I met with Uving animals, and these animals were always 

 Crustacea, Ophiura or Annelida. I usually found the first in the 

 water drawn up either from channels or at some distance from 

 the shore. The second were under stones, or in the masses of 

 seaweed. It was especially to the Annelida that the Fucus owed 

 its brilliancy. 



These results explained all the circumstances of the first kind 

 of phosphorescence. The Crustacea, whose movements are ener- 

 getic and whose locomotion is extended, cannot easily be col- 

 lected in sufficient quantity on a given point to have their scin- 

 tillations appear like a uniform tint. Besides, there is nothing in 

 the habits of the species I have examined to lead one to suppose 

 that they are inclined to collect in numerous bands. The size of 

 the Ophiura prevents such an idea with regard to them ; and the 

 smaller Annelid for a like reason cannot contribute to such a 

 result. Thus the light produced by these different animals is 

 always seen in points more or less near each other, but never 

 really blended. 



h. At Boulogne, on the contraiy, we find this brilliant light 

 exclusively due to Noctiluca. With the most careful examina- 

 tion, I have never found in my vases a single Annelid, or a single 

 phosphorescent Crustacean. 



Many circumstances, some of which will be explained hereafter, 

 illustrate the particular mode of phosphorescence of the sea, ren- 

 dered luminous by the presence of these Rhizopodes. We wiU 

 first notice their size and great number. The diameter of these 

 Noctilucce varies from about ith to |^rd of a millimetre ; but their 

 abundance more than compensates for their minuteness, each 

 drop of water, as observed by Suriray and M. Verhaeghe, con- 

 taining one or more. The following calculations will give some 

 idea of their vast numbers. 



In taking up some water at random from a brilliant wave, I 

 filled a tube about a decimetre in height. After being left a little 

 time quiet, the deposition of Noctilucce on the surface of the 

 liquid was about 1| centimetre in thickness. Thus the Nocti- 

 lucce composed about yth of the phosphorescent water. Again, I 

 took the water from the surface and filled a vessel about one- 

 half. The whole height of the liquid was about 15 centimeti-es, 

 and that of the mass of Noctilucce was about 5 centimetres ; here 

 the proportion was about ^. Finally, I remember that at False 

 Bay, M. de Tessan found the proportion equal to |. From these 

 numbers, it is easy to understand how the sea, rendered luminous 

 by the Noctilucce, may present a uniform brilliancy, irresistibly 

 impressing the idea of a phosphorescent solution. When the 



