212 Canon Tristram on the Polar Origin of Life. 



species inhabiting the Pacific Islands, of which some thirteen 

 have been ah'eady described, varying from black to brown, 

 some with grey, ashen, or buff heads ; but all small of stature, 

 and all having an unmistakable family resemblance, and all 

 sedentary in their respective islands. But the Blackbirds 

 were among the last of the Turdidce to leave the far north. 

 They had become comparatively acclimatized, as well as dif- 

 ferentiated ; and in this way we may account for the absence 

 of this group of TurdidcB fi'om the Ethiopian fauna, the 

 Blackbird finding the temperate climate of Europe adapted 

 to its needs, and being therefore not tempted to push further 

 south than the MediteiTanean coasts. At the time of the 

 emigration of the Blackbirds the accumulation of ice may 

 have commenced in the glacial epoch on the West Atlantic 

 coast, and consequently no species of this group occur in 

 North America. 



But there were probably two previous principal epochs of 

 emigration of the Turdidse from the north. The first and 

 earliest would seem to have been that of the genus Oreocincla, 

 the least differentiated of the family. These earliest emi- 

 grants only made a partial exodus, and that down the line 

 of Eastern Asia. They seem to have emigrated before the 

 family had become sufficiently differentiated to lose in ma- 

 turity the spotted plumage of the young. As is well known, 

 all the Orcocinche, alone of this family, retain the same 

 markings through life. Some of the emigrants soon halted, 

 penetrating no further than Japan and China. These retained 

 their attachment to the place of their origin ; and to this day 

 Oreocincla varia, while retiring even as far as the Philippines 

 in winter, returns to Siberia for nidification. From China 

 one party penetrated to the Himalayas and sent colonies 

 along the central mountain-ranges down to Ceylon. All 

 these soon learned to content themselves with a seasonal 

 vertical migration, like the subsequent settlements of Black- 

 birds. Others reached Formosa and there remained, while 

 others, finding the plains and valleys too hot, pushed further 

 south, even to Australia and Tasmania, leaving a few settlers 

 on each island on their route, which have gradually become 



