JONES : MOLLUSCAN ALBINISM. 5 
albino mollusc, in the general conchological acceptance of the 
term, is not an albino at all. The coloured mollusc, carrying 
an albino shell, is, indeed, in precisely the same position as the 
polar bear, mentioned above. ‘There are, also, shells which are 
partly albino and partly typical in colour. I have two speci- 
mens of the shells of Planorbis corneus, taken at Birch, which 
were partly white and partly typical in colour. Mr. Moss and 
Mr. Cairns have similar specimens from Ashton-under-Lyne. 
Examples of this curious abnormality have also occurred among 
the terrestrial mollusca. Capt. W. J. Farrer has taken a speci- 
men of Helix hispida at Bassenthwaite in Cumberland, the last 
whorl of which is albino, the others are typical. I took, also, a 
specimen of A. rufescens, at Matlock, presenting the same 
curious condition. Mr. Standen possesses a specimen of C/au- 
silia rugosa, the apex of which is white, the rest typical. There 
are other instances, but these are sufficient for illustration. The 
rule seems to be that a shell, having started typically, 
finishes as an albino, for most of the above present this con- 
dition ; there are, of course, exceptions. 
The cause of the above remarkable phenomenon I do not 
exactly know; it is, however, I think, due most probably to 
constitutional weakness 1n the animal, and not to lack of some- 
thing in the food. Were the latter the case, instead of finding 
single individuals presenting the above remarkable character- 
istics, we should find colonies representing the condition. 
That food, however, does influence the colouring of the 
shell in a very remarkable manner, I have experimental evidence 
to prove. My friend, Capt. W. J. Farrer, took at York Aelix 
arbustorum var. fusca and H. hortensis var. olivacea, both in con- 
siderable quantities. Having transported the specimens, which 
were about half-grown, to Bassenthwaite, he commenced feeding 
them upon cabbage-leaves. All that portion of the shell in both 
species which has been formed since their arrival at Bassenth- 
waite is pure white. Obviously something is wanting in the 
food supplied to them—that something may possibly be a cer- 
