114 Amos W. Peters. 



IV. DISCUSSION OF RESULTS. 



The preceding experiments demonstrate that the power of 

 phosphorescence is located in the mature animal solely in the 

 region of the paddle plates. I am not aware of direct evidence 

 for a more precise localization than that just given. Allman 

 ('62, pp. 518-519) and Chun ('80, p. 195) attributed this phenom- 

 enon in Beroe to the germinal cells lying in the walls of the gastro- 

 vascular tubes. The supposed fatty, phosphorescent substance 

 of Panceri according to Chun ('80, p. 195) does not exist. 

 Phosphorescence was observed by A. Agassiz ('74, p. 371) in 

 embryos. 



The experiments described in this paper also show that this 

 property belongs to protoplasm that has but little organic differ- 

 entiation, viz: that of the earlier stages of segmentation. When 

 we inquire what service in the economy of the animal is rendered 

 in the process of phosphorescence we find it difficult to give a 

 satisfactory reply. I have never been able to obtain phosphor- 

 escence in mature ctenophores without the motor activity of the 

 paddle plates, but not every movement of these is accompanied 

 by phosphorescence. Darkness and mechanical agitation are the 

 two selective stimuli whose joint presence results in phosphores- 

 cence. This important fact, taken in connection with the localiza- 

 tion of the reaction, the acceleration of its appearance by mechan- 

 ical agitation, and its complete inhibition by extremes of tempera- 

 ture, lead to a probable conclusion regarding its nature. The 

 phosphorescence of Mnemiopsis is a metabolic reaction which is 

 dependent upon the formation of a substance in darkness, the 

 katabolism of which takes place upon mechanical stimulation 

 and becomes observable as the energy of light. The amount of 

 substance so accumulated may be exhausted by continued mechan- 

 ical stimulation in darkness or may be consumed as produced. 

 When the animal is brought into the light the substance is no 

 longer produced or, if so, it undergoes katabolic transformation 

 rapidly, or the energy is given out in some other form than light. 

 That the phosphorescent substance cannot accumulate in the 

 light is shown by the fact that ctenophores removed from bright 

 daylight or sunlight to darkness are not immediately phosphores- 

 cent. This is the case whether they have been previously agitated 

 or have remained undisturbed. 



