MEANS OF DISPERSAL. 137 



phorus^ Alycceiis, Helicina, and Diplommatina, have a 

 very wide distribution/ It seems probable, however, 

 that large arboreal snails, even those which live in the 

 highest branches, may possibly be carried from place to 

 place when several trees are drifted off together in the 

 form of a floating islet. Some kinds adhere firmly to 

 the branches when hibernating, and others shelter 

 themselves among the epiphytic vegetation. Bulimus 

 fasciatus, a large species which lives on the branches of 

 trees, attaches the mouth of the shell very strongly to 

 the bark by means of a thick opaque secretion which 

 hardens to the consistency of glue, and in tearing the 

 animal away the bark or the shell is fractured sooner 

 than the secretion. Bulimus undatus^ also, another 

 large arboreal snail, attaches itself by means of a similar 

 glutinous substance, which, though exposed to wind 

 and rain, forms a perfect adhesion and protection to 

 the animal and only yields to its own solvent powers 

 on the approach of spring. These, and other species 

 with similar habits, may almost certainly, as already 

 suggested by Mr. Simpson, be carried in safety over 

 the sea on floating trees the higher branches of which are 

 borne above the crest of the waves, and it even seems 

 likely that they may float safely for moderate distances 

 in the sea itself adhering to detached branches, etc. 

 Both the species above mentioned are enumerated by 

 Dr. Binney among shells believed by him to have been 

 introduced by currents from Cuba to the southern part 



^ " Animal Life," ed. 4, 1890, pp. 287-8. 



