Phosphorescence in Ctenophores. Ill 



the phosphorescent condition could be removed by excessive 

 mechanical agitation. Reduction of intensity had frequently 

 been observed after long continued agitation. 



2.22 p. m. Strong phosphorescence. 



2.42 p. m. Phosphorescence appears only in slight gleams, but 

 these persist upon stimulation with the glass rod. 



The result indicates that sufficiently long-continued agitation 

 reduces the intensity of phosphorescence, but does not entirely 

 inhibit it. 



Experiment 5. The object of this experiment was to determine 

 whether the rate at which the ability to phosphoresce is acquired, 

 varies with the intensity of the light. Lots A and B each with six 

 ctenophores, were exposed to direct sunlight for five minutes. 

 The temperature of the sea-water before the exposure was 21°. 5 

 C; after it, 22°. 5 C. Then A was kept in the dark-box until 

 phosphorescent, being tested at intervals (/. e., not continuously 

 agitated). During the same time B was exposed to diffuse day- 

 light and at intervals it was placed in the dark-box for a momen- 

 tary test. B did not phosphoresce during the whole experiment 

 (19.5 minutes). A phosphoresced first after three minutes in the 

 dark-box, and though kept in diffuse daylight, it retained its 

 phosphorescence over five minutes, after which it lost its phos- 

 phorescence so long as it remained in the light. 



The result indicates that the ability to phosphoresce is acquired 

 more quickly in darkness than in diffuse daylight and also that 

 phosphorescence has a proportionate relation, in a negative sense, 

 to the intensity of the light. 



Experiment 6. Preceding experiments have shown that: (i) 

 darkness is at least one necessary condition for phosphorescence; 

 (2) darkness alone does not result in phosphorescence; and (3) 

 mechanical agitation can call forth and accelerate this phenom- 

 enon in the dark. This comparison suggested the question. Can 

 agitation alone produce phosphorescence } To make this deter- 

 mination a lot of ctenophores were poured repeatedly from one 

 dish to another in diffuse daylight and were tested at intervals in 

 the dark-box. The agitation including the tests was continued 

 for a period often minutes. No phosphorescence whatever could 

 be detected. The inability of agitation to produce this phenom- 

 enon was frequently observed. ' 



