248 
School, has very kindly carried out the bac- 
teriological experiments upon: which these re- 
sults largely depend. 
LAWRENCE J. HENDERSON , 
Wotcorr Gipps Memoria LABORATORY, 
HARVARD UNIVERSITY 
A MICROSCOPIC TRAP 
WHILE examining a very rich culture of 
Protozoa, recently, I saw a living animal 
caught in the smallest trap that I have ever 
heard of, about 1/18 mm. in length. The 
animal was a small Infusorian, . apparently 
Colpoda cucullus Miil., as well as could be 
determined in its cramped position in the trap. 
The trap was an empty shell of a small species 
of Arcella. 
The Infusorian had apparently entered the 
opening of the empty test and then, after the 
manner of a fish in a trap, kept swimming 
around and around the periphery of its prison, 
thus never coming to the centrally placed 
opening. I watched it pretty constantly for an 
hour and a half and it apparently never 
ceased, for more than a second at a time, its 
Fic. 1. A small Infusorian trapped in the empty 
shell of a fresh-water Rhizopod, Arcella. Camera 
lucida; X 630. 
forward or backward motion, except that, oc- 
easionally, it halted its progressive movement 
and. whirled around rapidly, at a rate of 100 
per minute, upon its median transverse axis. 
After being under observation for an hour 
and a half it suddenly became quiet, and, but 
for the contraction of its vacuole about every 
SCIENCE 
TN. 8S. Vou, XLVITI. No. 1236 
25 seconds, it seemed to be dead. Then it 
suddenly resumed its swimming and whirl- 
ing motions, which were continued, with oc- 
casional resting periods, till observations 
ceased at the end of the day, 24 hours from 
the first observation. 
The slide had been sealed with oil to pre- 
vent evaporation of the water, so that the next 
morning the culture was in good condition, 
but the prisoner had escaped, during the night, 
from its trap. 
The figure is a camera drawing, showing 
the animal in the trap, bent to the right, and 
indented on that side. 
ALBERT M. REESE 
WEST VIRGINIA UNIVERSITY 
A NIGHT RAINBOW 
A most wonderful display of aurora borealis 
was visible on Mount Desert Island last night 
and had the moon not been at first quarter the 
brilliancy of the display would undoubtedly ~ 
have been still greater. It had its base on a 
long, dark, unbroken band abutting on the 
northern horizon and shot upwards toward the 
zenith in innumerable streamers of vast reach, 
lengthening and shortening and shifting like 
the beams of a gigantic searchlight. Suddenly 
at about 10:40 P.M. a band like a gray-colored 
rainbow darted across the heavens near the 
zenith, passing from northwest to southeast 
and ending at a point near but not at the 
horizon. Though it may be common I have 
never seen the aurora span the heavens in that 
fashion. It looked like a vast single-span 
bridge. Beginning west of Arcturus it passed 
midway between Lyra and Aquila and ended 
far down in the southeast. At its midpoint 
overhead it was about as wide as the line join- 
ing the three conspicuous stars of Aquila. It 
seemed to be lower than the firmament, creat- 
ing the impression of pulling the sky down- 
ward and giving a limit to space. Unlike the 
streamers first seen it did not suggest a search- 
light but rather a band of delicate gray veil- 
ing, shining, yet not luminous—a night rain- 
bow. It was densest near the zenith but even 
there the stars were visible through it. 
For about thirty minutes little change could 
