1892.] 



THE BRITISH NATURALIST. 



35 



were exhibited by the members named : — Varieties of British Lepidoptera, the 

 president; varieties of Etipithecia vennsata, Mr. C. S. Gregson ; hfe history of the hot 

 fly (Gastrophilns cqiiij, Mr. R. Newstead ; Pliycis splciulidclla, captured at Wallasey, 

 July, 1891, Mr. H. B. Jones ; a fine web formed by the larvae of Ephislia clutella, Dr. 

 J. W. Ellis; and Scotch Dasydia obfuscaria, Noctna sobrina, Mr. C. E. Stott. 



— F. N. Pierce Hon. Sec, 143, Smithdown Lane, Liverpool. 



/ 



Mollusca. — Notes. 



Notes on Varieties.— A number of causes may be recognised as 

 constantly at work producing variation among the Mollusca. Some 

 varieties have established themselves as more or less permanent races. 

 According to my own observations banding and colour among the 

 Helices are the most permanent varietal characteristics, especially the 

 former; of course crossing may, and no doubt does cause endless 

 variation in these respects, but in breeding H. iienioralis and H. 

 Jiortensis from like parents 1 have found them in\ariabJy j roduce 

 young of the same colour (varying only slightly in shade) and banding 

 as themselves. In this respect they appear to come as true as the 

 different breeds of domestic poultry. Tlie difficulties of geLting 

 Helices to breed in confinement and still more of rearing tiiem from 

 the egg are great, and my successes in this way iiave not been so 

 numerous as I could have wished, but in every case in winch 1 have 

 succeeded in rearing the progeny of like parents, to such a stage that 

 the colour and banding could be determined, 1 have found these like 

 those of the parents, 1 expect to find during my experiments, which 

 I am still continuing, exceptions to tins rule, if only as re\ ersions to 

 some ancestral form, still, so far, the results have been 111 favour of 

 true breeding in these respects, and what is more singular, 1 have not 

 succeeded in breeding, unless each snail has belonged to the same 

 variety. This seems to indicate a preference among these animals 

 for mating with those of like colour and banding to themselves. As 

 bearing on this subject, no doubt every collector has noticed the 

 general similarity among snails of these species taken in any given 

 locality. With one of the slugs, A . ater, 1 had a different experience 

 as related in a former article. 



Some variations appear to be the result of congenital defect, as the 

 albino varieties and those with translucent bands. The only example 

 of any Helix of the latter kind which I have ever taken occurred in a 

 ditch about three miles from this place, this was var. liyalozonata of 

 H. nemoralis, and although I have searched the same and adjacent 

 localities several times every year since I have never found another. 



