I40 TPIE DISPERSAL OF SHELLS. 



within them in winter-time : Vertigo edentula^ for in- 

 stance, as Mr. Jeffreys mentions, is then to be found 

 in such stems, together with Carychimn minimum , and 

 other minute shells.^ Thus concealed, the creatures 

 would be buoyed up and protected in some degree from 

 contact with the w^atcr. It seems probable also that 

 entirely unprotected individuals, when swept from river- 

 banks during floods, or chancing to fall into the water 

 at ordinary times, might occasionally be carried in 

 safety to considerable distances, for they sometimes 

 float on the surface and are never immediately drowned. 

 Kinds which I have tried - have generally floated when 

 the animal was extended from the shell. A specimen 

 of Helix aspersa, in this condition, for instance, thrown 

 into the river Lud, floated freely with the current, but 

 I soon lost sight of it. Fifteen specimens of H. 

 hortensis, with the animals fully extended, all floated. 

 The creatures sink, however, as a rule, if tried when the 

 animal is entirely withdrawn ; thus, of ten specimens of 

 H. nifescens, all sank with the exception of two in 

 which the animals were extended, and these, tried again 

 when they had retired into their shells, sank also. But 

 this is not invariably the case : of thirteen specimens 

 of H. Jiortensis, for instance, placed in water when the 



^ '* British Conchology," i. (1862), pp. xxxiv., 269, 301 ; and see 

 J. E. Harting, "Zoologist,'^ (3)> ii- (187S), 125. In gardens near 

 Sydney, Mr. Musson tells me, Helix aspersa often takes up its 

 abode in the hollows of cut bamboos. 



^ Helix aspersa, hortensis, ajimstorum, riifescens, Sec. ; freshly 

 collected specimens for the most part. 



