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 larvae of Geoinetra 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 

 rohovavia 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 cratcegata. 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 larvae were more 

 sensitive to dark surroundings than to green. 



But the most remarkable results were given by caterpillars of 

 Amphidasys behdaria. 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 larvae 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 larvae 

 to be dark, but were not so effective as the twigs. Dark objects not 

 in contact with the larvae (piled around the cylinders containing the 

 food) had no effect. Among green leaves and shoots only, the larvae 

 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 larvae 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 



