192 Trans. Acad. Sci. of St. Louis 
Here is more evidence of delightful clearness; the moths 
which, when half a day younger, remained indifferent, now under 
identical surroundings, respond to the extent of 54 per cent of 
their number, to the light stimulus. The second group, those 
now two days old, had increased their efficiency from 64 to 85 
per cent; the third group, still in their prime, improved upon 
their old record only slightly, while the oldest, now verging on 
senescense, were beginning to wane. During the night 3 more 
females became travellers, and next morning three pairs of the 
moths were in copulo on the window sill. Unfortunately, I did 
not ascertain whether the air in the room was in motion. 
Exp. 26. June 29, 10:45 p.m. In the previous experiment, 
we found the males going to the window and the females follow- 
ing, but after all we do not know whether the latter responded 
to the light rays or followed the odor trail to the males. For 
this reason we wished to repeat this test in a room where no males 
were present, and to make the conclusions absolute, in a room 
where there was no possibility of male odors lingering about the 
windows. Therefore the family meekly submitted to ejection 
from still another room in the house, this time the living-room, 
which was transformed into an improvised laboratory. All 
windows were darkened excepting one in the southeast corner, 
likewise facing east, and 54 moths were placed on the wall in 
the northwest corner. There were 13 females 14 day old, 5 were 
one day, 17 were 2 days and 19 were 5 days of age. All were 
marked and placed on the wall at 10:45 p. m. 
The next morning revealed but slight activity during the 
night; only two moths (aged 2 and 5 days) had reached the 
window, three had moved about a foot toward it, and about @ 
dozen had crept upward a few inches on the wall. This seems, 
when compared with the previous test, a rather discouraging 
result. However, one must not lose sight of the fact that the 
others had rested all day and had done practically all of ther 
moving between 8 and 9 o’clock, while these had not even been 
placed on the wall until after that hour. 
At 9 a. m., all were replaced on the wall, but none moved to 
the light during the day. Between 8 and 9 p. m., their cus- 
tomary hour, their agitation began; 43 moved all or part Way © 
to the window; only 11 remained on the wall, and these moved 
slightly. Of course they were now one day older than recorded 
