MEANS OF DISPERSAL. 1 59 



times found little cakes of earth adhering to the feet of 

 wagtails, wheatears, or whinchats, shot, as he assured) Mr. 

 Darwin, on their first arrival on our shores, and before 

 they had alighted.^ Mr. Wallace, we find, dealing with 

 the origin of the land-shell fauna of the Azores, ex- 

 presses the opinion that some kinds may have reached 

 the islands " with the earth that often sticks to the feet 

 of birds," " and every one must admit that transportal 

 in this way is at least possible. 



Another possible mode of transport, already hinted 

 at, is suggested by the following passage, from pages 

 326-7 of the " Origin," referring specially to the dis- 

 persal of seeds : — 



" The crops of birds do not secrete gastric juice, and 

 do not, as I know by trial, injure in the least the ger- 

 mination of seeds ; now, after a bird has found and 

 devoured a large supply of food, it is positively asserted 

 that all the grains do not pass into the gizzard for 

 twelve or even eighteen hours. A bird in this interval 

 might easily be blown to the distance of 500 miles, and 

 hawks are knozun to look out for tired birds, a?id the con- 

 tents of their torn crops might thus readily get scattered!' 



That the " sudden deaths to which great numbers of 

 frugivorous birds are annually exposed must not be 

 omitted as auxiliary to the transportation of seeds to 

 new habitations," had already been remarked by Sir C. 

 Lyell, who suggested that birds with recently picked up 

 seeds still in their crops would now and then chance to 



* " Origin," p. 328. 



^ " Island Life," p. 247, ed, 2, p. 256. 



