t()iC>- CoLGAN. — Phototjopisni and Eye-Spots hi Linens. 9 
days later, having focussed the brood of worms at one 
point on the wall of the dish by the method just described, 
the cover was again placed over the dish with the opening 
at the side farthest removed from the worms. After an 
exposure of twenty -five minutes the worms were found to 
have crossed the dish and assembled themselves in a dense 
group opposite to the opening. 
The next experiment was made in diffused daylight. 
On this occasion the hole in the covering box was reduced 
to \ inch diameter and placed, not at the side, but at the 
top, so that the light impinged on the surface of the water 
not far from the edge of the dish. After an exposure^ of 
ten minutes five of the worms were found floating foot 
upwards on the water surface immediately beneath the 
hole admitting the light. After a further exposure of twenty 
minutes all the worms were found densely congregated 
beneath the hole, most of them floating on the surface, 
the remainder clinging to the side of the dish near the 
surface. As the worms had been evenly scattered over 
the bottom of the dish at the beginning of the experiment, 
they must have travelled across the bottom and up the 
side so as to reach the surface at the point where the light 
entered. 
In the next experiment a larger dish 3J inches in diameter 
was used. Having collected all the worms into a dense 
group at one side of the dish by the use of a perforated 
cover, as in the second of this series of experiments, the 
dish was turned through half a revolution so as to separate 
the group of w^orms by the whole diameter of the dish 
from the opening in the side of the cover box. After five 
minutes' exposure nearly all of the worms had crossed the 
dish and assembled themselves directly opposite the light 
opening. Another three minutes' exposure and the laggards 
had made good the crossing and joined the family group. 
This experiment was immediately repeated by another 
reversal of the dish, while the cover retained its original 
i The word " exposure " used here and in connection with the following 
experiments is to be taken as meaning exposure to diffused daylight of 
the orifice in the box while the box covers the dish with the worms. 
