l6o THE DISPERSAL OF SHELLS. 



be seized by hawks or eagles^ which, " soaring across 

 hill and dale to a place of retreat," might, after devour- 

 ing their prey, leave the seeds to spring up and flourish 

 in a new soil/ Now, as birds of many kinds are known 

 to feed largely upon snails, which, no doubt, often re- 

 main alive for some hours in their crops, it seems almost 

 certain that these causes may have operated, very 

 rarely, perhaps, for the dispersal of land molluscs ; and 

 even fresh-water kinds, though many are thin-shelled, 

 may also have been thus transplanted, but much less 

 frequently, for the restoration of an animal in this man- 

 ner to a fresh-water habitat is sure to be extremely rare 

 and exceptional. Mr. Cordeaux tells me that after a day's 

 shooting he has frequently opened the crops of birds and 

 found them to contain both land and fresh -water snails, 

 but, like several other ornithologists who have informed 

 me of similar observations, he is unable to say positively 

 whether any of the creatures were alive. Twenty 

 specimens of a Succinea, peculiarly packed together, 

 and four of Ptipa viuscornvi were once found by Mr. VV. 

 H. Dikes in the crop of a bearded titmouse {Pariis 

 biarniicus) ; all the shells, it is said, were uninjured, but 

 it is not stated that any were observed lo be alive." 

 Many birds, it ought, perhaps, to be mentioned, are 

 careful to kill the animals upon which they feed ; thus, 

 for instance, Mr. O. V. Aplin has seen a tame magpie 

 breaking the shells of rufous-snails {Helix riifescens) — 



' "Principles," ed. 9, (1853), pp. 624-5. 



^ W. H. Dikes, Loudon's " Mag. Nat. Hist.," iii. (1830), p. 239 ; 

 and see D. Cooper, Charlesworth's (n.s.), ii. (1838), p. 479. 



