154 THE DISPERSAL OF SHELLS. 



the air out of sight, and that observed in Maryland 

 carried leaves to such a height that they appeared 

 reduced to the size of flies. It is clear enough, I think, 

 from these facts that molluscs — even large and heavy 

 kinds — particularly those living among vegetable debris, 

 dead leaves, and the like, may frequently be carried 

 from place to place during whirlwinds, and it has even 

 been suggested also that those inhabiting open plains 

 or pastures may similarly be caught up and conveyed. 

 The idea that snails — Helix virgata, for instance — some- 

 times descend in showers, may have originated in some 

 cases, Mr. Jeffreys thinks, *' in a whirlwind having caught 

 up a number of them by sweeping along a grassy plain 

 and dropping its contents in a limited area." ^ 



Animal Agencies. 



Animals of various sorts in all probability, as we 

 have seen, have been actively engaged in the dispersal 

 of fresh-water molluscs, and this remark holds good, no 

 doubt, for terrestrial kinds. Something, there is reason 

 to suppose, has been done even by insects. Under 



^ "British Conchology," i, (1862), pp. 211-12. For a popular 

 allusion to wind-dispersal, see Dickens in the "Chimes" : " Toby 

 himself all aslant, and facing now in this direction, now in that, 

 would be so banged and buffeted, and touzled, and worried, and 

 hustled, and lifted off his feet, as to render it a state of things but 

 one degree removed from a positive miracle, that he wasn't carried 

 up bodily into the air as a colony of frogs or snails or other port- 

 able creatures sometimes are, and rained down again to the great 

 astonishment of the natives, on some strange corner of the world 

 where ticket-porters are unknown." 



