372 MR. E. B. POULTON ON THE COLOUR-RELATION BETWEEN EXPOSED 
An examination of the dates at which pupation took place in A. and C. unfortunately 
shows that in nearly all cases an important part of Stage III. had elapsed before the 
larvae were pinned on the frames. It is quite clear that A., 6, 8, and C., 6, 8, 9, 
cannot have been influenced after the transference, and there were probably only two 
larvae in A. (3, 4), and two in C. (1, 5), which may be considered to have satisfied the 
conditions of the experiment. The larvae which were found to have pupated by 12 p.m., 
September 4, cannot have passed as much as 13 hours on the frame, and most of them 
must have had a very much shorter period of time. The larvae of B. and D., on the 
other hand, seem to have passed the whole of Stage III. on the frame, and one of the 
most curious and exceptional things in all the experiments recorded in this paper is 
the fact that the larvae of D., surrounded entirely by black for the whole stage, should 
be lighter than those of A. or D., which were also partially exposed to gilt, and 
had been on the frame for a much shorter time in nearly all cases. In other respects, 
however, an analysis of the few results in which the influences had worked for an 
adequate period of time is very satisfactory. 
Degrees of colour. 
(1) 
(2) 
Very 
dark 
(3) 
Dark 
(3) 
(3) 
Light 
(3) 
Very 
light 
(3) 
(4) 
(5) 
A. Larger skin area in black, smaller in gilt for 
1 
1 
= 2 
Stage III. 
0. Larger skin area in gilt, smaller in black for 
2 
- 2 
Stage III. 
B. Entirely exposed to gilt for Stage III. 
5 
1 
= 6 
D. Entirely exposed to black for Stage III. 
3 
2 
1 
= 6 ! 
It is interesting to analyse in a similar manner 
the results of A and C., including those which had 
pupated at 12 p.m., September 4. 
A. 
1 
7 
1 
- 9 
C. 
1 
2 
3 
4 
=i°; 
The comparison between A. and C. in the upper of the above Tables confirms the 
results of the previous blinding experiments, showing that no sense-organ in the head 
can possess the property of being influenced by light in such a manner as to direct the 
formation of colour in the pupa. Conversely, the results strongly favour the view, 
and, in fact, confirmed as they are by other experiments, render the conclusion certain, 
that such a power is possessed by some terminal organ in the skin or by some one 
of its elements without the intervention of the nervous system. The former is the 
more probable hypothesis, for, if otherwise, we should expect to find diversely coloured 
pupge corresponding to the different colours in the immediate surroundings, but I do 
not regard this argument as convincing ; and the investigation of the structural basis, 
and the nature of the physiological processes which take place, afford a subject for 
research which promises results as interesting as the work itself will be difficult. The 
