BARBOUR, MATTHEW'S "CLIMATE AND EVOLUTION" 5 



cult}^ in surviving in a limited area. Trinidad, a large island separated 

 by a very narrow strait from Venezuela, has a reasonably full quota of 

 mammalian inhabitants, while the large and heavily wooded island of 

 San Miguel, just off the coast of Panama, has but a few small mammals, 

 quite a contrast to Coiba Island, farther north off Honduras, where even 

 a peculiar deer is known still to occur, Gorgona Island, ofE Colombia, 

 also with luxuriant vegetation, has a peculiar Cebus {Cebus curtus 

 Bangs), a peculiar Proechimys, and so far as knovni no other mammals. 

 Yet these differences are all among islands on the shelf and near or fairly 

 near the shore ; and I could multiply the examples ! 



Kow I do not believe, with Matthew, that the Antilles are oceanic 

 islands — islands which have received their fauna by fortuitous trans- 

 portal. My reasons for thinking as I do are these : First, I believe that 

 the islands of the Antillean chain have too evenly distributed and homo- 

 geneous a faima for it all to have been fortuitously derived; secondly, I 

 consider the fauna to be composed of too many different animal phyla; 

 and thirdly I believe that many of these elements are not of a nature to 

 have withstood "flotsam or jetsam" dispersal. We must now consider 

 Matthew's exposition of the natural raft hypothesis (p. 206 et seq.). He 

 states: '^"1) Natural rafts have been several times reported as seen over a 

 hundred miles off the mouths of the great tropical rivers such as the 

 Ganges, Amazon, Congo and Orinoco. For one such raft observed, a hun- 

 dred have probably drifted out that far unseen or unrecorded before 

 breaking up.^' This is obvious and imdoubted. But, and this is most 

 important, these rafts, even the very large ones, float low in the water; 

 they soon become soaked with salt water in a calm sea, rippled over or 

 broken over if the sea be choppy or rough as it is in the trade wind or 

 monsoon belts. Only organisms or their eggs Avhich are encapsulated or 

 otherwise naturally resistant can withstand these conditions. Molluscs 

 are stimulated to activity by dampening, but most are killed by salt 

 water — although some such as Cerion are resistant. Seines and Gekkos 

 show by their distribution that they may be carried about in this way. 

 Amphibians, amphisbsenians, naked gastropods, earthworms, fresh-water 

 fishes or crayfishes, Peripatus and a host of such delicate^ creatures simply 

 cannot withstand salt water. No such creatures have ever been observed 

 upon any raft, of the very few recorded, and to transport cyprinodonts, 

 ampullarias and the host of other fresh-water types one meets with in 

 Cuban ponds, for instance, the raft would have to include a puddle, at 

 least, of fresh water. Supposing that an amphisbanian, to take a good 

 example, withstood an ocean voyage upon a raft, how would the landing 

 take place? The raft would have to make a haven and then ground in 



