Phosphorescence in Ctenophores. 1 13 



Lot B was then removed to the ice bath whereupon the animal 

 became, after some time, phosphorescent. Hence the previous 

 cessation of phosphorescence was not due to death. 



Experiment 2. The aim and methods of this experiment were 

 the same as in Experiment i. 



Lot A at 21°. 5 C. was strongly phosphorescent; after 6.5 min- 

 utes cooling it was much diminished, and after 13.5 minutes 

 (9° C.) there was no phosphorescence. Lot A was then placed 

 on the warm water-bath and in 13 minutes became again phos- 

 phorescent. 



Lot B at 21°. 5 C. was strongly phosphorescent; after seven 

 minutes warming the phosphorescence was much diminished, and 

 after ten minutes (38° C.) there was none. At this temperature 

 the animals had completely disintegrated. 



Experiinent j. The aim and methods of this experiment were 

 the same as in Experiments i and 2. 



Lot A, strongly phosphorescent at 2i°.5 C, was cooled in ten 

 minutes to 9°. 5 C. and became non-phosphorescent. 



Lot B, strongly phosphorescent at 21°. 5 C, was cooled in 12.5 

 minutes to 11°. 5 C. and became non-phosphorescent. 



Another series of experiments was made to determine the effects 

 of variations of a few degrees only from the normal. Such varia- 

 tions, of from one to four degrees above and below the normal 

 (2i°.5 C), showed, in all the trials but one, a diminution of phos- 

 phorescence as compared with a control. In other words, phos- 

 phorescence in the dark-box appeared sooner in the animals at 

 normal temperature than at any other temperature. It would 

 not have been surprising to find an optimum point slightly differ- 

 ent from the normal temperature. The experiments made upon 

 this subject are not regarded as conclusive. 



The general result of this work upon temperature may be 

 stated as follows : 



The phenomenon of phosphorescence in the ctenophores here 

 investigated occurred during a range of temperature extending 

 from about 9° C. to 37° C, with an optimum at or near 21°. 5 C, 

 which was the temperature of their native sea-water. The inten- 

 sity of phosphorescence diminishes as physiological extremes of 

 temperature are approached. 



