Experiments in Rhythmetic Periodicity 169 
Exp. 14. The seven moths mentioned above plus three more 
wild ones were allowed to rest until 5:30 p. m. the next day ; 
the box was carefully covered to exclude the light. In the late 
afternoon, 5:30 p. m., the daylight was supplemented by a 50- 
watt electric light about twelve feet from the box. After hav- 
ing gently placed all the moths at the dark end of the box, the 
curtain was lifted at the end nearest the light. In three min- 
utes, three males had made their way to the lighted end, and 
after ten minutes I counted seven there. This movemnt was 
certainly due to the difference of light and not to the period of 
day, for this was not their normal time of activity and the con- 
trols in other cages did not show any activity at that hour. Of 
course the controls were exposed to the light of the room all 
ay. 
During the forty minutes when the moths were subjected to 
the light from one end of the box only these seven responded 
to the lure of the light, so at 6:10 the moths were all quietly 
Placed at that end of the box and covered, and the blankets 
lifted at the opposite end, which was not so brightly lighted 
since it did not directly face the electric light. During the first 
ten minutes, three males fluttered to the lighted end, and after 
twenty-five minutes, eight were there. These did not flutter so 
wildly as they had done in the first part of the experiment, 
but one cannot expect intense activity indefinitely. But their 
Sensitiveness to the light was unquestionably demonstrated first 
by their going to the lighter end of the cage, and second by 
crowding into the lightest corner of that end as they settled to 
rest. Some critics might say that a part of this activity may 
be attributed to imitation; that a few of the moths are super- 
sensitive to the rays of light and become active on slight stimu- 
lation, and the others follow by imitation or simply by being 
disturbed. This is by no means the first experiment in which 
we have found that a small proportion of the moths remained 
persistently quiet while their brothers all about them became 
active; hence we have reason to believe that each individual 
reacts when and only when he himself is physiologically or 
psychologically ready. : 
Exp. 15. The above was of course a test of the reaction of 
the moths to the dim light; now we shall see if they react like- 
wise to bright light. If the dim lights and shadows of evening 
