1902 Snails in Winter 31 



believe that relatively fewer young than old snails die during 

 a hard winter " from natural causes " or from cold; but the 

 very important task of constructing a Registrar- General's 

 Report for the lower animals has as yet hardly attracted 

 sufficient attention, and the data remain to be collected. 



All species do not exhibit the same reaction to cold 

 weather. When we are full of certain knowledge on the 

 matter, this portion of our subject should be one of very 

 great interest. At present we know so little that most 

 of our thoughts are the merest statements of ignorance. 

 Different species may, and presumably do, differ from one 

 another in (i) their power of heat regulation, and (2) the 

 body temperature at which they are able to lead an active 

 life. How far the former consideration is to be taken 

 into account, it rests with an untouched field of experi- 

 mental investigation to tell us in an exact way. It is also 

 only along the lines of exact research that we can hope to 

 discover what part the different factors play in determin- 

 ing the habits of each species. In the present state of 

 our ignorance it may be permissible to speculate a little. 

 In the first place, the colours of the species may have some 

 influence. Snails with dark -coloured shells would prima 

 facie seem less well fitted to withstand exposure to cold 

 than similar species of lighter colours, in which heat radia- 

 tion should be reduced by the pallor of their surface tints. 

 The observation that Xerophila virgata does not hibernate 

 is an old one, and it is not altogether true. This and other 

 species of the white-and-black group included in our English 

 Xerophila may show well-marked periods of hibernation. 

 On the other hand, there is no doubt that these species — 

 especially perhaps X. virgata and X. caperata — frequently 

 manifest a degree of resistance to the cold which is remark- 

 able. On the whole, it is more probable that their pale 

 colouration is correlated with a life spent in exposed situa- 

 tions under the rays of a hot sun, rather than with any 

 particular power of enduring frost. It must be borne in 

 mind, however, that the bare commons and similar localities 

 which this group especially affect, while perhaps very hot 

 during the daytime, are liable to be very cold at night. 



The varying habits of different species may also be referred 



