314 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1925 



considerable number of Hawaiian forms, for example, being derived 

 from a few American ancestors. Many of the seed plants, birds, 

 and some insects were derived from Central American ancestors.-'^ 

 But a lar<^e enough percentage of the forms are so Asiatic as to 

 have led those scientists who have examined this j)articular typ(i 

 of evidence to doubt if the existing distribution can be explained 

 on the basis of existing conditions. They have shown, for example, 

 that a favorable wind (the prevailing trades) and current (the 

 drift set in motion b}' the trades) should have given Hawaii many 

 Californian and Mexican forms of littoral mollusca, if these agencies 

 were effective in transporting these forms.'' Likewise, the believers 

 in the theory of widespread lands and certain other workers point 

 out that the prevailing winds and currents throughout the Pacific 

 tropics are westward, and the mnnerous species of Asiatic descent 

 must have advanced eastward against the prevailing winds and 

 currents. Yet the wind and currents are the only important agencies, 

 aside from nuin, that miglit have transported the plants and aniuials 

 in question from island to island. 



HOW HURRICANES CAN DISTRIBUTE LIFE 



Is it not highly probable that tropical cyclones have played a 

 part in the dispersal of life from island to island in the Pacific? 

 Upon their equatorward side there are often violent westerly winds, 

 completely overcoming the prevailing easterlies. As pointed out 

 in discussions of the courses followed, many storms move eastward, 

 within the tropics, or just beyond the tropics.^ In moving east- 

 W'ard, the strong westerly wind on its equatorward side carries 

 much with it, and sets up a strong drift as well. An illustration of 

 the occasional power and persistence of this westerly wind is given 

 by the renowned missionary John Williams, who, driven by canni- 

 bals from Herve}' Island, drifted in an oj)en boat 500 miles to 

 Tahiti with a constant westerly wind.^ Normally, easterlies prevail 

 in that portion of the ocean. 



The power of the wind to transport light objects through the air 

 is frequently illustrated during hurricanes, as, for example, when 

 land birds and insects are carried out to sea in large numbers. 

 Indeed, the presence of butterflies and birds far out at sea has 



^ Brown, F. B. H., " Oilgln of Hawaiian flora," Proceedings First Pan-Pacific ScienUfic 

 Conforoncc, vol. 1, pp. 131-142, 1920 (seed plants) ; Muir, F., " Some problems in 

 Hawaiian entomology" (insects), ibid., and Henshaw, "Fauna ITawaiiensis," volnrae 

 vertebratos (birds). 



8 Muir, F., loc. cit. 



' Visber, S. S., " Tropical cyclones of the Pacific witb charts of tracks," Monthly 

 Weather Bevlew, Vol. 50, pp. 288-297, 583-589, 1922, and Bulletin 20 of Bishop Museum 

 of Honolulu, 1925. 



» Williams, John, " ilissiuiiary Knterpri.scs In tlu> South Sea Islands," London, 1838. 



