COLLINGE: COLOUR VARIATION IN SOME BRITISH SLUGS. 237 



reared to maturity ; of these 



27 were typical A. subfuscus. 



4 var. griseus. 



5 var. succineus. 

 7 var. krynickii. 



2 allied to the var. laterithts. 



One of the var. lateritius was paired with a var. succineus from a 

 former brood, and eighteen of the progeny were reared to maturity, 

 of which seven were referable to the var. succineus and five to the var. 

 lateritius. 



Incidentally, some interesting colour variations were obtained in 

 the foot-fringe of the different varieties. As no useful purpose would 

 be served by describing these, I meiely give the number of variations 

 for each species and variety : — 



Avion empiricorutn - - - 22 



var. castanea - - - - 14 



var. hiberna - - - - 5 



var. rufa - - - - 12 



var. n/ba - - - - 3 



var. albolateralis - - - 14 



Ariofi subfuscus - - • - 15 



var. griseus - - - - 6 



var. succineus - - - 14 



var. lateritius - ' - 12 



Malacologists would seem now agreed to allow a species or variety 

 to vary within a certain limit, and to discountenance sub-species and 

 sub-varieties. It is, and always will be, a difficult matter to say where 

 the limiting line should be drawn, particularly so with beginners or 

 those with little experience. The longer one devotes attention to 

 these interesting molluscs, the clearer does it become that the endless 

 sub-varieties rather impede than facilitate progress. 



So far as the two species of slugs here dealt with are concerned, 

 it would appear that even the well-marked colour varieties are less 

 stable or constant than we have hitherto supposed, and that the 

 minor colour variations are almost endless in number and of little 

 importance to the student of malacology or zoology. 



Pyramidula rotundata m. sinistrorsum in Bucks. — On July nth I found 

 a small sinistral Pyramidula rotimdata at Burnham Beeches, among dead leaves. 

 This piece of ancient forest shelters a very interesting set of molluscs, — J. E, 

 Cooper {Read before the Society, Sept. 9th, 1908). 



