208 
Mr. Rolfe, writing in 1884, favored the former of Wallace’s views, but 
states that “geological evidence will probably in future throw much light 
on this point.” 
It appears to the writer that Wallace’s later view is more nearly in 
accordance with the facts. He was familiar at that time with the 
presence of submerged banks connecting the now isolated groups, but he 
did not have any paleontological evidence. 
Rolfe repeatedly speaks of migrations of southern types from the 
Malayan and Australian regions northward to the Philippines, but from 
lack of material he was unable to discuss the great infusion of northern 
types which must have migrated southward from Siberia, and even 
North America, through Japan, south China, and Formosa, and which 
are found in the highlands of northern and central Luzon. 
The writer, accompanied by Mr. Merrill, botanist of this Bureau, has 
recently made the ascent of some high mountains in northern Luzon, 
where many species of plants identical with, or closely related to, those 
of Formosa, southern China, and Japan were observed, and also some 
identical with North American forms, which apparently have migrated 
from that region by way of the Aleutian Islands, Japan, and Formosa to 
Luzon. 
That there have been in the past repeated land connections between 
Japan and North America, by the closing of Bering Straits, has sub- 
stantially been proven by the periodic migrations of molluscan faunas 
between those regions in past geologic periods.? Of course, at the 
inauguration of the glacial period these plants and animals would 
migrate far to the south and even into the Tropics. It is expected that 
future paleontological work will corroborate this view by revealing a 
decided infusion of Japanese forms in the molluscan fauna of the 
Pliocene and Pleistocene beds. 
If there were such a land connection in Miocene times, as we have 
already indicated, it is probable that it continued nearly to the time of 
the present flora, previous to which disruption may have taken place 
through volcanic disturbances, this break occurring early enough, how- 
ever, to allow sufficient time to elapse during which the flora and fauna 
of these Islands could take on their present insular aspect. 
We should not fail here to refer to work in a somewhat different 
field—namely, to the investigations on the distribution of the avifauna 
in these Islands—made during a number of years by Messrs. Worcester 
and Bourns.'* Although their work gives evidence of a great break 
between the Philippine and Bornean groups, we do not believe their 
"J. P. Smith: “Periodic Migrations Between the Asiatic and the American 
Coasts of the Pacifie Ocean,” Am. Jr. Science (1904), 17, page? 
“Dean C. Worcester and Frank 8. Bourns: “Contributions to Philippine 
‘Ornithology.” Proce. U. S. National Museum (1898), 20, 549. 
