VARIATION IN COLOUR. 
91 
strated that a Helix can exist even when its organic connection with 
tlie shell is completely severed. 
It is quite certain that local circumstances do at times conduce to 
the development of albine shells. One instance will suffice to sup- 
port this view ; under stones in a dell on the cliffs near Hele Bay, 
Ilfracombe, Mr. Brockton Tomlin, in March, 1887, found hundreds 
of the white variety of Helix rotundata, and it is suggestive that 
this state was practically universal and not confined to this particular 
species, but was shared in by the associated species, Hyalinia celUiria 
and Avion hovtensis. This variation, so plentiful within these narrowly 
circumscribed limits, was not met with elsewhere in the neighbourhood, 
clearly showing that the influence, whatever its nature, did not ex- 
tend beyond the limits of this little valley. 
Amongst Lepidoptera Mr. Poulton has satisfactorily shown that the 
character of the larval food affects its colouring. He especially 
instances Triphwna, pronuba fed in darkness upon the midribs of 
cabbage leaves, which were ({uite unable to form the green and brown 
colouration, although others fed under similar conditions upon more 
normal food were typically coloured. Moquin-Tandon considered one 
of the principal causes of albinism in mollusks to be the nature of the 
soil and consequently the food, and as some corroboration of this 
opinion it may be stated that M. Jules Colbeau long ago observed and 
recoi'ded that about Dinant the translucently-banded Helix hovtensis 
exhibited a noticeable partiality for gooseberry bushes, and Mr. A. E. 
Boycott has recently remarked upon the predilection of this and 
other albine forms for plants of the horse-radish, but although these 
observers did not pursue the investigation further, yet it has been 
actually demonstrated by Capt. W. J. Farrer that this albine modifica- 
tion may sometimes be of a phytopliagic character as a change of diet 
in connection with the different environment of captivity proved 
to be sufficient to cause albine growth upon shells previously almost 
melanic in colouring. A number of half-grown shells of Helix 
hovtensis var. oUmcea and Helix avbiistovuni var. fasccc were 
gathered at York and conveyed to Bassenthwaite, in Cumberland, and 
there fed to maturity in captivity upon the leaves of turnip and 
cabbage, the new growth in both species was of quite an albine 
character and the junction of the contrasting colours sharply defined ; 
but Mr. T. Scott has recorded an almost exactly opposite experience, 
a young Helix m'bustovum ysx. Jlavescens fed upon cabbages, turnips. 
