DIURNAL PERIODICITY OF PITOSPHORESCENCE. DA 
Organisms. he indifferent set containing the majority of the 
phosphorescent organisms were also practically indifferent to candle-light. 
In regard to numbers of organisms in each set, the positive set were by far 
the most numerous, and the numbers in the indifferent and negative sets 
were about equal. 
The experiment was varied in a fresh tow-netting by placing several 
flat pie-dishes containing the organisms (not separated off on this occasion 
as to phototaxis) around the lamp in the photographic room, just after 
nightfall, until the usual phototactic groups had separated, then 
extinguishing the lamp, and watching the spontaneous appearance of 
phosphorescence without disturbing the dishes. There is no spontaneous 
phosphorescence for a period of about two minutes under such 
circumstances, then it commences, and 1t 1s seen that the phosphorescent 
organisms are scattered about indiscriminately in each dish, and not 
arranged in any relationship to where the light had previously been. 
Sometimes the phosphorescing organisms are moving about rapidly while 
illuminated, but in the majority of cases they are almost or quite at rest, 
and it is probable that if there had been any previous movement of a 
phototactic character while the lamp was lit, the arrangement would not 
have quite disappeared in the short interval after the light was 
extinguished before the spontaneous phosphorescence reappeared. 
The only conclusion from the experiments appears to me to be that 
these particular phosphorescent organisms are almost or quite indifferent 
to incident light. 
B.—Divurnat Prriopiciry 1n PHOSPHORESCENCE 
The suggestion of the work described in this section arose incidentally, 
as above-mentioned, and at the time the experiments were made it was 
unknown to me that a diurnal periodicity in phosphorescence had 
previously been observed and described. 
A search through the earlier literature, however, revealed a 
description of its occurrence in Pyrophora by Aubert and R. Dubois,! 
and in Noctiluca by Massart.?_ Henneguy® states that Noctiluca does not 
1. Compt. rend. acad., T. XLIX, p. 477, 1884; Compl. rend. soc. d. biol., p. 661, 1884. 
See also papers in both these Journals by Rk. Dubois, 1884-6. 
2. Bulletin scientifique de la france et de la be/gique, 1. XXV, p. 72, 1898. 
3. Compt. rend. soc. d. biol., XL, p. TO7, 1884. 
