24 M. de Quatrcfages on the Phosphorescence of 



neous or provoked. Often also it appears under the form of 

 repeated sparks, following eaeh other in quick succession, under 

 the influence of the will, and very similar to electric sparks. 

 Often, but not always, there is formed by this production of 

 sparks, a mucilaginous humour, gelatinous or aqueous, which is 

 diffused around in great abundance, and is evidently placed in a 

 secondary or passive state of phosphorescence, which continues 

 a long time without requiring any new influence from the organic 

 being, and even lasts after that has been divided or destroyed. 



A light which to the naked eye ajipears uniform and tranquil, 

 shows itself scintillating under the microscope. 



5th. The viscous humour which envelopes and penetrates the 

 ovaries seems to be especially susceptible of acquiring this com- 

 municated light, which is constantly reinforced by friction, and 

 reappears even when it seems to have ceased. 



May not the light emitted by living fishes, by Actinias, and 

 by many other animals covered with mucosity, be sometimes 

 merely communicated ? 



6th. The relations which exist between the production of light 

 and the sexual functions are evident in the Coleoptera, although 

 the connexion of the small luminous sacs with the reproductive 

 organs may remain concealed. With many marine lierma])hro- 

 dite animals, phosphorescence appears to be a means of defence 

 and protection, analogous to those of another kind which exist 

 in the Brachinus crepitans, the cuttle-fish, the frog, or to the 

 discharges of the torpedo. Whatever it may be, the air and the 

 sea have their phosphorescence. 



7th. As yet it is only among the Annelids, and of them only 

 in the Photocharis, that a peculiar phosphorescent organ has 

 been discovered ; it is external, tufted, frequently giving out 

 light, similar to a thick cirrus, showing a largely cellular struc- 

 ture, and formed within of a nmcilaginous substance. The ex- 

 panded base of the marginal cirri in the Thaumantias (Acalephs) 

 may be regarded as phosphorescent organs, of an unusual kind. 

 The ovaries are more probably luminous, passively and in a 

 secondaiy manner, although their minuteness and transparency 

 have prevented our ascertaining whether the organs of phos])ho- 

 rescence are placed near them, as for instance in the Polyno'e 

 and Pyrosoma. 



8th. The production of light is evidently a vital act very simi- 

 lar to the development of electricity, an act which being com- 

 pletely individual, becomes more feeble and ceases on too fre- 

 quent repetition, which reappears after a short inte^-val of repose, 

 to the production of which absolute integrity of the organism is 

 not necessary, but which sometimes manifests direct connexions 

 only with the nervous system. 



