XXXII 



Individuals — leads to widely divergent, or even directly opposite results, litde 

 value can be attached to them. Not a few, even of the more important ones, 

 are governed by the suggestion of mimicry which, like every suggestion, not 

 unfrequently induces one to observe what is looked for sothat one cannot be 

 too careful in this respect. Others again, some of them of great importance, 

 are completely dominated by the preconceived notion that the colour mani- 

 festations must be explained by chromo-photographic action. The correctness 

 of this idea, however, is also ver)' doubtful and this should constantly be borne in 

 mind. Without losing sight of this we will proceed to examine these observa- 

 tions. 



The fact that where a caterpillar at a specific period of its existence, when 

 it ceases feeding and prepares to pupate, is exposed to radiation from any 

 definitely coloured environment — especially during the twenty hours preceding 

 the last twelve hours before pupating — the colour of the resulting pupa 

 frequently adapts itself to its surroundings, may at the outset be accepted as 

 having been proved beyond dispute, especially by Pox:lton's investigations. It 

 further appears, however, that much difference in this respects exists amongst 

 the various kinds of caterpillars. 



Of the older observations on this point, those made in 1876 by Mrs. Barber 

 are well known especially through Darwin having drawn attention to them. 

 According to this observer pupae of Papii.to Nireus L. reared against a twig 

 of the citrus tree, on which the larva lives, were light green ; between 

 dark green leaves dark green ; against dead twigs covered with pale yellowish- 

 green leaves they resembled the latter; while they were yellowisch against the 

 wooden frame of the case of the same colour. Red surroundings appeared to 

 exercise no influence but on the other hand a pupa attached to the junction of 

 purplish brown brick and wood composing the case was stated to have its 

 back the colour ot the bricks and the under surface that of the wood. The 

 latter observation, however, was doubted by Poulton since it did not agree 

 with his own experience; he justly refers to the fact that it is a common 

 occurrence that the colours of pupae differ greatly in the dorsal and ventral 

 regions and when it is borne in mind — what has, moreover, been proved 

 in other instances — that Mrs. Barber was a fanatical supporter of the 

 then novel theor}' of mimicry, I consider it advisable not to attach too 

 much weight to her observations. Mr. Roland Trimen subsequently con- 

 ducted experiments, on the pupa of Papilio Demoleus L. He found 

 these pupae yellow, green, or reddish-brown, according to whether they 

 wefe attached to bands of these colours fixed by him to the sides of the cage. 

 A black surrounding caused them to become dark but light red and blue 



