304 MR. R. A. ROLFE ON THE 



Asiatic continent or not, there does not seem sufficient evidence to 

 show ; but at length a period of elevation set in, owing to volcanic 

 agency ; the ancient sea-bottom emerged from beneath the water, 

 and the subterranean forces burst through the sedimentary rocks, 

 burying them with the ejected scoria? and lava. A considerable 

 period would be required for this process ; and it is evident that 

 at length the islands — probably very different in configuration 

 and extent from what they are now — became connected in some 

 degree with the land which undoubtedly existed to the southward, 

 and where the typical Malayan flora probably originated. Mean- 

 time a more complete connection through the Archipelago than 

 at present had been favouring a migration from Australia west- 

 ward. The then existing species gradually migrated northward 

 through the Philippines, some reaching Mindanao, others Luzon, 

 and some passing through to Formosa, a few of which even 

 extended to Japan by way of the Loo Choo Islands. Some others 

 appear to have spread across from Formosa to South China and 

 Hong Kong, as Thi/sanotus chn/santherus, F. MuelL, the only 

 outlying species of a genus all Australian and with eighteen 

 others endemic in Australia. It is not necessary to assume that 

 the Australian and Malayan migrations were contemporaneous, 

 or that they passed over by one single connection ; on the con- 

 trary, a few species seem to have reached the Philippines by 

 direct communication with the Moluccas, at a time when circum- 

 stances did not allow them to reach either Java or Borneo. The 

 typical Malayan genera, however, seem to have passed direct 

 through Borneo, and perhaps some from Borneo itself. Besides 

 these connections there are evidences of a former direct connec- 

 tion with the north-eastern point of Celebes, by way of a sunken 

 reef, of which a few small islands are now the only remaining 

 trace. In support of this view it may be noted that the volcanoes 

 of Celebes are confined to the north-eastern portion ; and it 

 seems probable that the islets stretching away to the south- 

 eastern point of Mindanao are only volcanic connections between 

 the two. The present condition of the volcanic forces in the 

 Philippines probably differs only in intensity from that of the 

 past ; and, if this view be correct, it is evident that periodical 

 eruptions have taken place since the time of their emergence ; 

 these eruptions having been to a great extent local, sometimes 

 in one locality, sometimes in another, but formerly of gigantic 

 dimensions, — as is proved by the enormous volcanic mountains 



