GEOGRAPHICAL DISTRIBUTION. 33 



Letters of Charles Darwin,' iii. p. 159), " I do not believe that one 

 species will give birth to two or more new species as long as they 

 are mingled together in the same district." And the importance of 

 Isolation as a factor in the multiplication of species is over and over 

 again recognized by Wallace in his 'Island Life,' as the following 

 quotations prove : — " We " (p. 243) " have every reason to believe 

 that special modifications would soon become established in any 

 animals completely isolated under such conditions ; " and again 

 (p. 258), "however long they may have inhabited the islands, there 

 has been no chaaoe for them to have acquired any distinctive 

 characters through isolation." 



It is not known that any species of bird is peculiar to the Kurile 

 Islands ; but a local race of the Japanese Wren, Troglodytes fumi- 

 gatus kurilensis, has not been obtained elsewhere. Like the local 

 race of the European Wren found on the Faroe Islands, it is remark- 

 able for its long bill. The winters are very cold in the Kurile 

 Islands ; consequently few birds are resident, and the opportunities 

 for isolation are very small. 



Picas major japonicus is a local race confined to the three main 

 islands, but connected with the typical race by intermediate forms in 

 Sakhalien and the valley of the Amoor. Picus leuconotus S7ibcirris is 

 a local race principally confined to Hondo, but occasionally oc- 

 curring in Yezzo, though most examples from that island are almost 

 typical. Parus palustris japonicus is a, local race found in Kiu-siu 

 and Hondo, and represented by intermediate forms in Yezzo. 



One species only is supposed to be peculiar to Kiu-siu, Phasianus 

 smmmeringi ; but Strix uralensis fuscescens and lyngipicus kisuki are 

 two local races peculiar to that island. 



Very little is known of the Seven Islands, only twenty-two species 

 having as yet been obtained there, but one of these, Merula celmnops, 

 is peculiar to the islands. 



Still less is known of the island of Tsu-sima ; but one species, 

 Picus richardsi, has not been found elsewhere. 



Of the Loo-Choo Islands, the large island of the central group 

 and an island of the southern group are the only ones that have been 

 partially explored, with the result that several new species and three 

 local races have been discovered. lyngipicus kisuki nigrescens is a 

 local race peculiar to the islands; Hirundo javanica namiyei is 

 another peculiar local race ; and Hypsipetes squamiceps pryeri is a 

 local race only differing from the typical form in being on an average 

 slightly smaller. 



