MEANS OF DISPERSAL. 163 



intervals, on the surface of the ocean, to be uhimately 

 liberated, perhaps, on some distant shore. Large num- 

 bers of land-birds, I suppose, annually perish in the sea ; 

 their floating carcases, Darvvin states, sometimes escape 

 being immediately devoured,' and, as shown by Mr. 

 Ward's observation, a Helix can retain life in the crop 

 of a dead bird at least for three days. In such circum- 

 stances, of course, molluscs would be protected to some 

 extent from the evil influences of salt water, and, in 

 illustration of this point, it may be noted that a number 

 of seeds of peas and vetches (which are killed by a {q:\n 

 days' immersion in sea-water) nearly all germinated 

 after having been enclosed in the crop of a pigeon 

 which had floated on artificial sea-water for thirty 

 days." 



Various kinds of birds, it will be remembered, have 

 been observed to eject the contents of their crops when 

 frightened or wounded, as gulls and terns do when 

 pursued by the skuas, and it seems quite possible, as 

 Mr. Roberts has already suggested, that snails, still 

 alive, may occasionally be thus disgorged, and set down 

 in places perhaps some considerable distance from the 

 spot where they were picked up and swallowed. Mr. 

 Clement Reid suggests that a good deal may have been 

 done, also, by birds gorging themselves after a long and 

 wearying migration, and afterwards casting up the con- 

 tents of their stomachs, little injured, and perhaps a con- 

 siderable distance away, and he states that he has 



1 " Origin," p. 326. - " Origin," p. 326. 



M 2 



