28 The Field Naturalisfs Quarterly Feb. 



This epiphragm varies in composition and consistency in 

 different species : in the large "Roman snail," Helix pomatia, 

 it is very thick and strong, containing a considerable quantity 

 of inorganic material ; and along the edge a reflection of the 

 innermost part of the nacreous layer of the shell, of a partly 

 silicious character, is said to be often formed. In Cryptom- 

 phalus it is tough and leathery, usually dirty white-brown in 

 colour, but sometimes a beautiful pale-green. In most of 

 the smaller species it is quite thin and fragile. The snail 

 does not keep its body in contact with the inner surface 

 of this membrane ; it wisely interposes a layer of that warm 

 material — stationary air. The epiphragm may be multiple ; 

 in one specimen of C. aspersus I have counted as many as 

 seventeen which had been successively laid down as the 

 snail had retired farther and farther within its shell. A few 

 of our British snails have permanent doors to their shells : 

 Cyclostoma, for instance, has a very thick operculum ; and 

 Clausilia a fairly strong clausium, which would appear to 

 close the already much-reduced aperture quite tightly. It 

 is, however, very often accompanied by an epiphragm. 



Besides the actual cold, invertebrates have to make what 

 provision they may against those assaults of more active 

 animals to which the winter, with its period of enforced 

 quiescence, renders them particularly liable. As far as 

 snails are concerned, they are not in a much better position 

 to escape such enemies as birds and mice under favourable 

 meteorological conditions than during the winter. One of 

 the leading German conchologists encourages the flagging 

 spirits of the young collector with the remark that "snails 

 are not accustomed to escape by swiftness." Indeed they 

 are, as a rule, so much better hidden away during cold 

 weather that it is only the scarcity of other food, and the 

 consequently increased anxiety and energy on the part of 

 the birds in searching them out, which renders winter not a 

 more desirable time than summer. But it is probable that 

 the enforced rest of winter may lay many of them open to 

 fatal attacks by other invertebrate animals. Yet these are 

 not numerously active at that time of the year, and the 

 methods which are adopted to protect from the cold would 

 in large part appear to be probably effective against the 



