288 NATURAL SCIENCE. APRIL, 
placed among green leaves in darkness, and were darkened thereby, 
though not nearly so strongly as by dark surroundings in daylight. 
The larvee of Geometra papilionaria, which hibernate, were sensitive 
before the winter, when various shades of brown in colour; in the 
spring, however, when they become dimorphic, brown or green, they 
were found to be no longer sensitive. The caterpillars of Boarmia 
vobovaria were, before hibernation, dark grey or brown in a dark 
environment, and greenish among green leaves. 
Still more satisfactory results were obtained with caterpillars of 
Rumia crategata. These were dark brown among black twigs, and 
light brown with green patches among green leaves. Miss Gould (2) 
also obtained similar results with this species. A striking experiment 
by Poulton in the subsequent year seemed to show that there is no 
tendency of these acquired colours to be inherited ; indeed, the cater- 
pillars from eggs laid by moths reared from the darker caterpillars 
were more easily affected by green surroundings than by dark; while 
the offspring of moths reared from the lighter larvee were more 
sensitive to dark surroundings than to green. 
But the most remarkable results were given by caterpillars of 
Ampiudasys betularia. These were nearly all dark when many dark 
twigs were placed with the food, mostly dark when some twigs were 
inserted, and all green when no twigs were used. ‘The presence of 
white paper spills caused the larve to assume a remarkable whitish 
hue. In 1892, Poulton carried out a more detailed series of experi- 
ments on this species. Caterpillars among black twigs were found 
to be nearly or quite black, those among brown twigs were brown, 
those among dead leaves were mottled-brown with vein-like markings. 
Artificial dark surroundings (black paper or enamel) caused the larve 
to be dark, but were not so effective as the twigs. Dark objects not 
in contact with the larve (piled around the cylinders containing the 
food) had no effect. Among green leaves and shoots only, the larve 
always turned green (the early stages are always brown), except when 
they were much crowded, in which case they had rather a darkening 
effect on each other; it appears that dark surroundings act more 
readily than green. With dark and green environment in feeble 
light, similar results were obtained to some extent, but the differences 
were by no means so marked as in daylight. In darkness, no 
difference was produced, whatever the surroundings, the caterpillars 
being always black, brown, or grey of various shades. The presence 
of blue paper spills caused the larve to assume a dark purplish hue, 
while orange paper among the food leaves produced a green colour in 
the caterpillars. 
Poulton has shown that the dark pigments (to which the various 
shades of brown, black, grey, etc., are due) are deposited in the cells 
of the epidermis, while the green colouring-matter is found in the sub- 
jacent fat. The presence or absence of both sorts of pigment is 
determined by the surrounding objects, through some quality in the 
