12, TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
Examined again at night (8—9 p.m.) by lamp-light when nearly all}; 
the organisms in the plates come to the point nearest the ight. Shading | 
as before with shadow parallel to direction of incidence, gives a compact }j 
group in the illuminated half near the Lght, but a great many are in the 
darkened half which possesses a diffuse group at farthest point from light. 
Examined again April 23rd, noon (about forty-eight hours from 
commencement of experiment). Took ihe control plate of organisms into a 
south room having direct strong sunlight from an open window. ‘The 
organisms after a time collect very slightly to sun side, but in the quite 
open unshaded plate are fairly indifferent, being distributed all over. 
Now one-half of the dish was shaded by cardboard, the line of shade, as on 
previous occasions, being arranged parallel to incidence of the heht; at 
once all the organisms came out into the sunlit half, somewhat more at the 
point nearest to the sun. On reducing the sunlit part to a very small 
space, 1t became crowded with organisms accumulating more densely at 
the point nearest to sun. ‘This compact group of organisms was pipetted 
off from the white plate into a black vulcanite half-plate photographic 
developing dish, containing sea-water, when the organisms, at once almost, 
accumulate at the part of the dish farthest from the sun. The half of the 
black dish farthest from the sun, after stirring up, was covered over 
(that is, with the line of shade at right angles to plane of incidence), and 
the organisms all collect, at remotest end of shaded part, away from sun. 
This peculiar reversal in the black dish is difficult to explain, unless 
it was due to the absence of reflection. The result could not be repeated 
in other experiments because the organisms were never again found 
indifferent in sunlight, but always strongly negative, even in the white 
plates. 
The organisms in this experiment were observed for four days longer ; 
at the end of the third day they had become very strongly negative in the 
diffuse daylight of the north window, a reversion, it will be observed, from 
their original mixed condition with a large preponderance of positive 
organisms. While in this strongly negative condition they were taken 
into the dark room and tested with lamplight from a small oil lamp. At 
1. This is a very exceptional behaviour in sunlight. 
