266 Experiments upon the colour-relation, dc. 
insufficient. The light-coloured and green pup pro- 
duced by the clear glass are interesting, and confirm the 
general result of Myr. Poulton’s similarly-arranged 
experiment, showing that, on the whole, strong illumina- 
tion and the proximity of green leaves does produce 
these appearances. The pupe in experiment (A) show 
the effect of white surroundings. 
7. Conctustons.—The general results of these experi- 
ments may be shortly summed up as follows :— 
(a). Mr. Griffiths confirms Mr. Poulton’s observation 
that dark surroundings exercise a retarding influence 
upon the period before pupation. 
(b). In the failure of the attempted conflicting colour 
experiments (in which the colours added in Stage III. 
produced no effect), there is strong confirmation of the 
results of Mr. Poulton’s experiments on Pieris and 
Vanessa, which show that the freshly-formed pupa is 
not photographically sensitive, and that Stage II. is the 
time of chief susceptibility. Compare especially the 
results of the two sets of experiments with yellow 
(IV. A. and IV. B) in support of this, although these 
are only more striking than others because the yellow is 
itself a much stronger influence. 
(c). The general results of the colours themselves also 
entirely confirm Mr. Poulton’s experiences. This is 
notably the case with the dark pupe produced by black, 
the green pups produced by yellow, and the effects of 
ereen, and of white (as far as they go). ‘The pale 
colours, pink and light blue, probably acted as somewhat 
dusky white surroundings, producing indeterminate, 
but, on the whole, rather light, results. 
(d). The special effect of yellow surroundings in 
arresting the formation of dark superficial pigment, and 
in tending towards the production of green pup, were 
very striking, and confirm Mr. Poulton’s suggestion that 
rays from this part of the spectrum, when predominant 
in the light incident upon the susceptible larva, deter- 
mines the production of these results whenever green 
pup are produced by the influence of surroundings, 
viz., When, as in nature, green pup of Pieris are pro- 
duced on green leaves, that the effect is caused by the 
reflected yellow rays only. 
Although no new conclusions can be drawn from these 
