some Marine im trtebrata. 25 



The memoir of IMeyen is less extended, but it contains some 

 imjwrtant facts*. The author admits three kinds of phospho- 

 rescence : — 1 . The phsenomenon is owing to a mucosity diffused 

 in water. In that case the water seen in the day has a uniform 

 tint of bluish white. It is often observed in tropical ])orts, but 

 rarely out on the open sea. This mode of phosphorescence may 

 be produced artificially by washing or by crushing certain Mol- 

 lusks and Acalephs either in sea-water or in fresh. 2. Phospho- 

 rescence results from the presence of certain living animals, en- 

 dowed with a luminous mucus. This continues even after the 

 death of the animal; it arises from a supei-ficial oxidation of the 

 mucous coating, and it can be reproduced after it seems extinct 

 by passing the finger over the animal. The animals which owe 

 their luminous property to a secretion are, according to the 

 author, Infusoria, Rotifera, Biphoi-se, Medusje, Asterias, Cuttle- 

 fish, Sertularia^, Pennatuife, Plauarijfi, Crustacea and Annelids. 

 3. The third cause of phosphorescence is in some animals from 

 the presence of one or more special organs. Of this number are 

 the Pyrosoma, and especially P. Atlantica, whose light, of a 

 greenish blue, is very brilliant. Each individual carries behind 

 its mouth a soft opake substance, of a reddish brown colour. 

 This body is slightly conical, and under the microscope thirty or 

 forty red points may be seen ; it is this substance which pro- 

 duces the light. 



III. Observations. 



It is apparent from the foregoing statements, that the great 

 majority of naturalists, whatever explanation they have given of 

 the phosphorescent ])h8enomena, have aj)plied that explanation 

 indiscriminately to all cases. Meyen himself, while admitting 

 three kinds of phosphorescence, nowhere expresses the idea that 

 the production of light arises from causes essentially different. 



It is in this point, I believe, that the writings of these learned 

 men are deficient. In a note published in 1843 j, I endeavoured to 

 establish a diflerent opinion, and to show, that under the general 

 name of phosphorescence, phaenomena essentially distinct have 

 been confounded, and which have really nothing in common but 

 the production of light. We have already shown that such is also 

 the opinion of ]\I. Becquerel. After having renewed all that my 

 predecessors have written on the subject, after having made new 

 experiments and new observations, I am more than ever per- 

 suaded that it is really so. Without speaking of the phos- 



* Beitragc zur Zoologie, Ton F. J. F. Meyen, fiinfte AbhancUung. 

 Ueber das Leuchten des Meeres (Nov. Act. Nat. Cur. t. xvi. Suppl. 1834). 



t Note sur un nouveau mode de Phosphorescence observe chez quelques 

 Annelides et Ophiures (Ann. des Sc. Nat., 2e serie, t. xix. p. 183). 



