112 Anios W. Peters. 



This result shows that a non-phosphorescent ctenophore is not 

 made phosphorescent by mechanical agitation alone. Further- 

 more, comparison of all preceding experiments shows that dark- 

 ness accompanied by mechanical stimulation is at least one com- 

 bination of conditions which is able to produce phosphorescence, 

 but its two factors acting singly cannot produce this result. 

 Other stimuli capable of eliciting phosphorescence may, of course, 

 exist. 



2. Temperature. 



Experiment I. This experiment was made to determine the 

 effects of physiological extremes of temperature. It was per- 

 formed in a dark room. A pailful of fresh ctenophores standing 

 there at a temperature of 2i°.5 C. emitted, when jarred, enough 

 light to illuminate the room to a considerable degree. From this 

 supply four animals (lot A) were removed to the ice bath and four 

 others (lot B) to the warm-water bath. The respective cooling 

 and warming of the two lots was done simultaneously. The ice 

 bath consisted simply of a basin containing broken ice, in which 

 the vessel containing lot A was partly immersed. Neither ice nor 

 fresh water (from melting ice) came into contact with the animals. 

 They were gradually cooled in their original sea-water. The 

 other lot of animals (B) were warmed in sea-water by placing the 

 vessel containing them over sufficiently warmed water. The tests 

 for phosphorescence were made at intervals by stroking the 

 ctenophores as usual with a glass rod. The temperatures were 

 taken with the bulb of the thermometer in contact with the surface 

 of the animal. Since the phosphorescent parts, the paddle plates, 

 are superficial, the temperatures given apply to these parts. The 

 interior of the jelly might have been at a different temperature. 

 Under these conditions the following record was obtained: 



Lot A at 21°. 5 C. was strongly phosphorescent; seven minutes 

 later at I2°.5 C. no phosphorescence could be observed. A was 

 then removed to the warm-water bath whereupon the animals 

 became, after some time, phosphorescent. Hence the previous 

 cessation of phosphorescence was not due to death. 



Lot B at 21°. 5 C. was also strongly phosphorescent; five min- 

 utes later at 37° C. no phosphorescence was observable. 



