1890.] Recent. Literature. 931 
author quotes Mr. Skertchly as endeavoring to explain the origin of 
such coloration as follows : ** This theory ‘ presupposes (a) that danger 
is universal; (2) that some butterflies escape danger by secreting a 
nauseous fluid ; (c) that other butterflies noticed this immunity ; (d) that 
they copied if. The opinion expressed in the words I have italicised 
will hardly be accepted by a single naturalist. I imagine that even 
the American Neo-Lamarckians do not follow their founder so far as 
to believe that the volition of an animal could account for all the 
details of mimetic resemblance.’’ 
Both Mr. Skertchly and his critic illustrate the misunderstanding 
which may arise from a neglect of the physiology of the origin of 
variations. Yet the great value of the present work consists in the 
fact that it is a mine of information for the investigator in this direc- 
tion. Thus e 113 and afterwards are narrated the author's 
remarkable o on the imitation by the pupas of butterflies of 
the colors of the bodies to which they are attached ; experiments 
already commenced by Mr. W. W. Wood, Prof. Meldola, Mrs. McE. 
Barber, Mr. Mansel Neale, and others. Green, yellow, and reddish- 
brown surroundings were closely imitated by the colors of pupas of 
the same species placed in proximity to them. Mr. Poulton found 
with pupas of Vanessa urtice, which have normally some gilt spots, 
that when they were placed within black surroundings they were, as a 
rule, extremely dark, with only the smallest traces, and often no trace 
at all, of the golden spots which are so conspicuous in the lighter 
forms. He then tried white surroundings on 150 chrysalides. In this 
case ** not only was the black coloring matter, as a rule, absent, so that 
the pupas was light-colored, but there was often an immense develop- 
ment of the golden spots, so that in many cases the whole surface of 
the pupas glittered with an apparent metallic lustre," A gilt back- 
ground was then employed, with the result that a much higher percent- 
age of gilded reg and still more remarkable individual in- 
stances, were obtain 
That these results are due to the direct influence of the light 
reflected from the surrounding surfaces on the body of the pupas seems 
extremely probable. The analogy, suggested by Wood, to photo- 
graphic process, is probably correctly rejected by Poulton as an 
explanation, though that some analogous process is at work seems 
very probable. The fact that where the color when once produced 
cannot be changed by exposure to another color, urged by Poulton 
as s conclusively disproving Wood’s theory, has no such value, since 
the process is one which. is coincident with growth, and cannot be 
