PEARCE : VARIETIES OF BANDED SNAILS. 131 



Now, it becomes evident that any interest attaching to 

 what has been suggested as an interpretation of the markings 

 of Hehx caperata and its varieties is much increased and 

 widened, if we think that it may be appUed, perhaps, to explain 

 as well the marking and bandings of other and kindred 

 species. 



We have opened up to us a further field for investigation, 

 if we would seek to discover whether the bandings of the 

 typical form oiHelixvirgata, Helix ericetomin^ and of the variety 

 bizona of Bulivius acutu^ are to be attributed to the feeding 

 of sheep in the pastures, where these moUusca occur ; to 

 say nothing of the bandings of the kindred continental forms 

 like Helix ?ieglecta Helix variabilis, Helix pyrainidata, Helix 

 candidula, Helix cespitum, etc. These continental species seem 

 to vaiy in the same way as our Englisli banded forms, and 

 therefore we may infer, have the same cause or causes tending to 

 make them so to vary. 



To revert, in conclusion, to our species. Helix caperala, 

 which, with its varieties, has occupied our attention so far, we 

 can imagine that the development which the colouring and 

 marking have passed through represent to us a gradual change, 

 through mottled forms, from an original form which had an 

 uniformly brown shell, which tends, owing to the surroundings of 

 an arid, open, and sunny habitat, to a uniform whitish or white 

 shell, which we know is the prevailing characteristic colour of 

 species living in dry and sunburnt countries. 



The variety ornata being really an aside form, so to 

 speak, prominent only on the sheep pastures, arises from the 

 causes previously explained. Tims, to bring out the serial 

 connection between the forms, in accordance with the above 

 hypothesis, we may put all the variations into the following 

 table of arrangement : — 



