100 THE DISPERSAL OF SHELLS. 



for considerable periods must have been highly useful, 

 for we find that many kinds have learnt to evade the 

 cold of winter by hibernation and the excessive heat 

 and dryness of summer by aestivation, and thus they 

 have been able to overcome climatic conditions which 

 in other circumstances might have been fatal, and some 

 kinds, having learnt to continue the latter process for 

 great lengths of time, have been able to penetrate the 

 dryest deserts. It is important, of course, to inquire 

 also as to what extent the creatures are able to with- 

 stand the notoriously harmful effects of contact with 

 sea-water, for on this the value of certain suggested 

 means of trans-oceanic dispersal obviously depends ; 

 but I know only one or two facts bearing upon the 

 point, and these can be conveniently referred to in the 

 next chapter. 



One of the most remarkable cases of long-suspended 

 vitality I have anywhere seen recorded is given in 

 Bingley^s '^Animal Biography," vol. iii. p. 574,^ 

 where some snails — on being immersed in water — are 

 said to have recovered and crept about after an uninter- 

 rupted torpidity of more than fifteen years : — 



" Mr. Stuckey Simon, a merchant of Dublin, whose 

 father, a Fellow of the Royal Society, and a lover of 

 natural history, left to him a small collection of fossils 

 and other curiosities, had among them the shells of 

 some snails. About fifteen years after his father's death 

 (in whose possession they continued many years), he by 



^ As quoted by G. J[ohnston]., Loudon's" Mag. Nat. Hist.," vii. 

 (1834), pp. 1 13-14. 



