DIURNAL PERIODICITY OF PHOSPHORESCENCE. 33 
same with different intensities of light and different coloured lights, 
‘showing that the locomotor apparatus is not affected by the light, but 
‘continues to work at the same rate. 
7. The particular organism used (Nauplius of Balanus) moves from 
red light to blue ight, and from blue to green, under such circumstances 
that the incident light is the same im direction for both coloured regions. 
This would indicate that with the particular total intensities being used 
for the experiments, green is a more suitable or optimal stimulus than 
blue, and blue in turn more optimal than red. 
8. Movement in converging and diverging light is described and 
shown to be explicable on the basis of intensity of ight alone, and that 
direction produces its effecis in a secondary manner on account of the 
heht and shade effects of the animal’s own body. 
9. The phosphorescent organisms experimented with (certain 
copepods) were shown to be indifferent, in regard to movement, to light 
from without. 
10. That light from without has another type of influence upon these 
phosphorescent organisms is shown, however, by the fact that their 
periods of activity and rest in regard to phosphorescence follow 
respectively the hours of daylight and darkness. 
11. It is shown that this alternating diurnal periodicity can persist 
for a long period (twelve days) in absence of the accustomed recurring 
stimulus of the light and darkness of day and night. 
12. The phosphorescence of these copepods in captivity is 
spontaneous, and although increased by mechanical stimulation, it goes on 
vigorously even when the organisms are undisturbed and quite still. 
13. When the organisms are freshly taken, the character of the 
phosphorescence is such that a faint light persists, which is increased at 
intervals by bright flares or flashes. Ata later period the light disappears 
entirely between the flashes, which have a longer interval between them. 
Under probably pathological conditions, after the organisms have been 
kept confined for a considerable period, there may be lighting up of the 
organisms with a continuous glow. 
14. The appearance of the spontaneous phosphorescence at nightfall, 
