DIURNAL PERTODICITY OF PILOSPILORESCENCE. 27 
howed spontaneous phosphorescence. The display in the three Thursday 
lettings is not so vivid as on the previous night, there being fewer 
rganisms phosphorescing. It is also noticeable that the phosphorescence 
is not so vigorous in each individual organism. The flare out is perhaps 
as great, but the light completely dies out in all cases after each flare, and 
the period between the flares seems to be lengthened, so that one cannot 
pick out a particular organism by its flashes and keep track of it. The 
two dishes from the Wednesday tow-nettings, which are to-night showing 
for the third time, are not much decreased in vigour from the second 
night, either in frequency of spontaneous flashing or in vividness on 
stirring them. Nearly as many phosphorescing organisms appear to be 
present, and the flashes are about as bright as on the preceding night.! 
These Wednesday organisms have now lit up for the third time, 
having been quite quiescent in the intermediate periods of daylight in the 
outer world. One of the two dishes has been in complete darkness 
throughout the period. From this onward all the sets of organisms are 
kept in complete darkness the whole time. 
Saturday, September 26th.—The organisms were examined at 11 a.m., 
and again at 1 p.m., when no sparking was occurring, nor could any be 
evoked by vigorous stirring. The next observation was commenced at 
6-07 p.m., when the daylight was commencing to fade outside. The dishes 
were not stirred, but quietly watched in the complete darkness. When the 
first spontaneous flash occurred, the dark room was quitted and the time 
noted; it was 6-13 p.m. Between 6-15 and 6-30, six flashes were counted ; 
between 6-30 and 6-45, twenty-two flashes; between 6-55 and 7-15 p.m., 
there were twenty flashes. The display is much less marked than on the 
previous evenings. On stirring the dishes, three or four organisms can 
be made to phosphoresce at once in each case. 
The organisms on the Polysiphonia nigrescens ave also phosphorescent 
on stirring. 
Sunday, September 27th—Kxamined at 10-30 a.m.; no phos- 
phorescence, either spontaneous or on stirring, from any of the dishes. 
1. This was observed in nearly all the experiments, a great drop during the first twenty- 
four hours, and then a very slow death-rate in the residue. 
