330 
PROTECTIVE RESEMBLANCE. 
wanner and drier grouiul. (’)ii the Italian inonntains the transition 
fnnn the ordinary translncent glancous specimens found in the valleys 
to the intensely dark oi)a(pie siieciinens inhabiting the cold and 
cloudy nionntain regions can be clearly traced, and although these 
sombre forms may not be limited geographically to particularly humid 
regions or cold northern latitudes, yet their appearance is always in- 
dicative of the local or transient })eculiarities of their environment. 
Heat principally affects and increases the formation of the red 
pigment and under artificial conditions has been experimentally 
demonstrated by Simroth to inhibit the dermal disposition of the 
black pigment in Arion ater and Limax maxhnu!^ and also to favour 
the development of albinoes, the individuals, however, only remaining 
albine under a continuance of the warmth, while other specimens 
from the .same batclies of eggs reared under more natural conditions 
acipiired the colourings characteristic of the species. 
The re<l colouring matter, which has been shown to be to some ex- 
tent dependent u])on warmth for its production, has been .shown by 
Simroth to be probably a warning colour in xiriun, as many creatures 
to whom he offered xirion rufus as food either totally rejected it or 
ate only the viscera, and as the red i)igment is jirobably a waste 
product of the tissues, discharged by the dermal glands, this effect is 
not imi)robable. 
The pigmentation of the animals of our land and Huviatile mollusca 
does not generally e.xhibit any remarkable differences in the distribu- 
tion of the colouring, the variations being chiefly confined to 
dilferences in the intensity of the general colouring ; the greatest 
variety is shown by the naked species, which being fully e.xposed to 
the full effects of external inHueiices, are more cpiickly affected by 
and resi)onsive to changes in their environment and therefore exhibit 
greater diversity in the external pigmentation of the body. 
The Protective Resemblance of the animal or shell of various 
species to some natural oliject of the environment is due in a great 
measure to external coloration, the specially imitative mode of its 
distribution or arrangement being probably gradually acipiired by the 
preservation and perpetuation of those individuals most closely simu- 
lating the particular object. A strikingly coloured animal or shell, 
strongly contrasting with the surroundings amongst which the 
creature exists, must, unless it is otherwise protected, inevitably be 
more easily detected by its enemies, thus tending to the elimination 
