92 



PERFECT ALBINISM IN LIMAX ARBORUM Bouch.-Chant. 



By W. DENISON ROEBUCK, F.L.S. 



(Read before the Society, September nth, 1912). 



On the 27th day of August, 19 12, Mr. Charles Oldham, in com- 

 pany with Mr. Lionel E. Adams, found an albino example of the 

 Tree-slug on a beech tree in the woods near Berkhamsted, Herts. He 

 sent it to me the following day, and I showed it at the next meeting 

 of the Conchological Society. It is the most perfect example of 

 albinism in slugs that I have ever seen. It was entirely and abso- 

 lutely without external pigmentation, not even the eye-specks being 

 coloured. The only colour visible is that of the internal organs seen 

 through the skin, and the apparent very pale grey shade with white 

 mottlings on the sides of the body is merely the transparency of the 

 skin and not due in any way to pigmentation. The specimen was 

 ' not quite adult, and is now preserved in alcohol in the Conchological 

 Society's voucher-collection. 



The only previous examples we have seen were those taken near 

 the Botanic Garden, Old Aberdeen, by Mr. Geo. Sim and which Mr. 

 Taylor described ("Monograph," part 12, vol. 2, p. 274) as v^x. alba 

 Taylor, animal entirely creamy-white, except the black eye-specks, 

 no trace whatever of body or mantle-markings, but the dark internal 

 organs are dimly visible through the skin. 



The present example is clearly not referable to this, variety— which 



has pigmentation in the eye-specks. It is, therefore, necessary to 



describe it as a new variety, thus : 

 Limax arborum var. nov. albinos Roebuck. 



Animal entirely white, absolutely without external pigmentation, 



only the dark internal organs showing faintly through the transparent 



portions of the skin. 



It will be of interest to note that on the 14th September, atGrange- 



over-Sands (in v.c. 69, Westmorland-with-Lake-Lancashire), Mr. Fred. 



Rhodes took a fine adult example of Arion ater v^x. alba sub-var. 



simplex, wliich was the nearest approach I have seen to perfect 



albinism in that species — even the foot-fringe being' white and not 



yellow as commonly found. BuHhe eye-specks were coloured and 



there was the faintest tinge of pale grey on what might be termed the 



vertex of the mantle. 



