132 THE DISPERSAL OF SHELLS. 



gaining, by flight, some island of the newly-formed 

 group, while the seeds and berries of herbs and shrubs, 

 which fall into the waves, may be thrown upon the 

 strand. But if the surface of the deep be calm, and 

 the rafts are carried along by a current, or wafted by 

 some slight breath of air fanning the foliage of the 

 green trees, it may arrive, after a passage of several 

 weeks, at the bay of an island, into which its plants and 

 animals may be poured out as from an ark, and thus a 

 colony of several hundred new species may at once be 

 naturalized." ' 



Many kinds of snails, from the nature of their habitats, 

 seem eminently liable to be carried with floating trees, 

 rafts, etc. Large numbers, every one knows, hide 

 themselves beneath the bark of trees ; the Siiccinea 

 arborea, to give an instance, lives, Mr. Musson tells me, 

 on the inner side of the bark of gum-trees in Australia, 

 and is difficult to remove without breaking the shell ; 

 and several of our own snails — ClausiiicB, etc. — as every 

 conchologist knows, are often found in similar situations, 

 under the bark of old forest trees. Crevices within the 

 trunks of partially hollow trees are also favourite hiding 

 places for many kinds, and some are in the habit of 

 eating their way far into the decaying wood. The Rev. 

 L. Blomefield has described a pollard-elm pierced in all 



^ " Principles," ed. 9, 1853, pp. 640-2, quoting *' System of Geo- 

 graphy," vol. V. p. 157 ; Spix and Martius, "Raise, etc.," vol. iii. 

 pp. loii, 1013 ; Sir W. Parish's "Buenos Ayres," p. 187; 

 Robertson's " Letters on Paraguay,'' p. 220 ; and " United Service 

 Journal," No. xxiv. p. 697. 



