728 Sensibility to Light and Colour in [December, 
The number of the animals thus tested was as small as 
possible. The experiments were confined to one represent- 
ative of the normally eyeless groups, — namely, the earth- 
worm, — and to one representative of a blind animal, for 
which purpose the common water-" newt ” ( Triton cristatus) 
was selected. 
As regards the eyeless animals, the experiments, of which 
the author gives a brief abstract, are not of such a nature 
as to render further exaCt investigations needless. For his 
experiments on earth-worms he used a box consisting of 
perfectly equal and similar compartments or cells. The 
front and back of the box consisted of panes of quite clear 
glass, puttied water-tight in the framework. The latter 
was further provided with grooves for the occasional intro- 
duction of panes of glass and bottles with parallel sides. 
The cells had each a separate cover, and could be separated 
from each other by perpendicular slides. By introducing 
two slides the box could be divided into three compartments, 
each of which had two front and two back windows. The 
latter, however, were covered, so that the light was admitted 
merely from the front. The bottom of each cell was covered 
with mud, but in so thin a layer that the worms could not 
hide themselves in it. For obtaining different degrees of 
light the two windows were used, one being uncovered and 
the other darkened by the introduction of a slip of wood, or 
both were fitted with media of different colours. 
The experiments were conducted in the following very 
simple manner : — “At the beginning of each experiment a 
considerable number of worms (20 to 30), just dug up, were 
placed in each compartment, and were distributed as equally 
as possible over the entire surface. The box was placed at 
a window having a northerly aspeCt, and at regular inter- 
vals — in general every hour — the number of specimens in 
each of the differently lighted cells of each compartment 
was taken. The worms were then again equally distributed, 
and at the same time the position of the light-absorbing 
media was changed. From time to time, generally every 
four hours, the worms were removed, and fresh ones were 
substituted. 
The first experiment consisted in leaving these animals 
the choice between a relatively light and a comparatively 
very dark compartment. In seven enumerations there were 
found in the light compartment 40 worms, and in the dark 
one 210. The proportion of these two numbers, the 
" quotient of reaction,” is therefore 5*2. It may be asserted 
without any doubt that a strong light is very unpleasant to 
