EMIGRATION AND EVOLUTION. 123 



apparently in irruptic waves, but in steady chronic 

 tides. From south to north, from New Zealand to 

 Japan, stranded races, so closely allied in many cases 

 as to be almost conspecific, on almost every import- 

 ant island or group of islands, point the direction 

 emigration has taken, and suggestively indicate a 

 much more continuous land surface between the 

 Malay Archipelago, North Australia, and New 

 Zealand than is now the case. Thus Norfolk 

 Island is the home of Merula poliocephcda ; Lord 

 Howe's Island that of M. vinitincta ; New Caledonia 

 that of M. xanthopus ; the Loyalty Isles that of 

 M, mareensis (Mare Isle), and M. pritzbueri (Lifu. 

 Isle) ; the New Hebrides that of M. albifrons 

 (Eromanga Isle) ; the Fiji Islands that of iV/. hicolor 

 (Kandavu Isle), and M. tempesti (Taviuni Isle) ;. 

 the Malay Archipelago that of M. javanica ; For- 

 mosa that of M. albiceps. Here we have evidence 

 of emigration on a very extensive scale ; and testing 

 the antiquity of the movement by the close affinities 

 of the species, we are forced to the conclusion that 

 it occurred at no very remote period. It seems to 

 me that this emigration was not of a chronic 

 character, the result of a gradual increase of popu- 

 lation, slowly spreading from one island to another, 

 for all of the species are now sedentary, but rather 

 of an irruptic nature, caused by climatal change in 

 a southern centre of dispersal ; or even by the 

 concurrent gradual or even rapid submergence 

 of a continuous route of migration between New 

 Zealand and Japan, during a glacial period, which 



