the relations of Java and
Borneo to the continent, in which I took account of changes of land and sea
only; but a fuller consideration of the influence of changes of climate on
the migration of animals, has led me to the much simpler, and, I think,
more probable, explanation above given. The amount of the relationship
between Java and Siam, as well as of that between Java and the Himalayas,
is too small to be well accounted for by an independent geographical
connection in which Borneo and Sumatra did not take part. It is, at the
same time, too distinct and indisputable to be ignored; and a change of
climate which should drive a portion of the Himalayan fauna southward,
leaving a few species in Java and Borneo from which they could not return
owing to the subsequent isolation of those islands by subsidence, seems
{387} to be a cause exactly adapted to produce the kind and amount of
affinity between these distant countries that actually exists.

THE PHILIPPINE ISLANDS.

A general account of the fauna of these islands, and of their biological
relations to the countries which form the subject of this chapter, has been
given in my _Geographical Distribution of Animals_, Vol. I. pp. 345-349;
but since the publication of that work considerable additions have been
made to their fauna, having the effect of somewhat diminishing their
isolation from the other islands. Four genera have been added to the
terrestrial mammalia--Crocidura, Felis, Pteromys, and Mus, as well as two
additional squirrels; while the black ape (_Cynopithecus niger_) has been
struck out as not inhabiting the Philippines. This brings the true land
mammalia to twenty-one species, of which fourteen are peculiar to the
islands; but to these we must add no less than thirty-three species of bats
of which only ten are peculiar.[93] In these estimates the Palawan {388}
group has been omitted as these islands contain so many Bornean species
that if included they obscure the special features of the fauna.

_Birds._--The late Marquis of Tweeddale made a special study of Philippine
birds, and in 1873 published a catalogue in the _Transactions of the
Zoological Society_ (Vol. IX. Pt. 2, pp. 125-247). But since that date
large collections have been made by Everett, Steere, and other travellers,
the result of which has been to more than double the known species, and to
render the ornithological fauna an exceedingly rich one. Many of the
Malayan genera which were thought to