154 ANTHOZOA ASTEROIDA. 



not deemed two phenomena so significant as to the non-elec- 

 trical nature of the light of the Pennatula, as to render repeti- 

 tion of experiments needless. The one of these is the well- 

 known fact that electricity produces light only when passing 

 through or across a non-conductor, such as air. It is impos- 

 sible, accordingly, to produce even the faintest luminous ap- 

 pearance in water, or a saline solution conducting a current, 

 however gigantic the machine or battery supplying it be. I 

 need only mention the failure of experiments with the friction 

 machine in damp weather, to recall this fact. It is still more 

 interestingly manifested by the circumstance that the electrical 

 fishes are not in the least luminous, nor does any flow of light 

 accompany their electrical discharges. On the other hand, it 

 is only with difficulty, and after carefully insulating them, 

 that small sparks are obtained -from the torpedo or silurus ; 

 and the spark is obtained, not in the water, but out of it, that 

 is in air. 



" When a Pennatula is plunged into fresh water, it throws 

 off", or detaches from itself, many calcareous spicula covered 

 with mucus. Each of these phosphoresces, and continues to 

 do so for hours, even for days. If any one affirm that these 

 minute shiniug points are alive, I will not dispute the point 

 with him, but will only ask at his hands some consistent 

 theory which shall reconcile with known facts the possibility 

 of the continuous luminosity of detached particles, such as the 

 spicula are, depending upon electrical excitement. To main- 

 tain as much light, for so long a time, by any electrical 

 instrument with which we are acquainted, even in the best 

 non-conductor, would require an expenditure of force quite 

 enormous. Everything I know of electricity is at variance 

 with the possibility of such an expenditure of force being at 

 work. I hold myself, therefore, justified in having never re- 

 turned to an experimental inquiry into the cause of the phos- 

 phorescence of the Pennatula. 



" On the whole I believe it 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. 



" The known relations of carbon and hydrogen to combus- 

 tion are such as to make it quite possible, and even probable, 



