But there is another set of facts, which help us on another step towards the case of the Javanese mountain flora. On the higher slopes of the Himalayas, on the tops of the mountains of Central India and of Abyssinia, a number of plants occur which, though not identical with those of European mountains, belong to the same genera, and are said by botanists to represent them; and most of these could not exist in the warm intervening plains. Mr. Darwin believes that this class of facts can be explained in the same way; for, during the greatest severity of the glacial epoch, temperate forms of plants will have extended to the confines of the tropics, and on its departure, will have retreated up these southern mountains, as well as northward to the plains and hills of Europe. But in this case, the time elapsed, and the great change of conditions, have allowed many of these plants to become so modified that we now consider them to be distinct species. Avariety of other facts of a similar nature have led him to believe that the depression of temperature was at one time sufficient to allow a few north-temperate plants to cross the Equator (by the most elevated routes) and to reach the Antarctic regions, where they are now found. The evidence on which this belief rests will be found in the latter part of Chapter II. of the "Origin of Species"; and, accepting it for the present as an hypothesis, it enables us to account for the presence of a flora of European type on the volcanoes of Java.
It will, however, naturally be objected that there is a wide expanse of sea between Java and the continent, which would have effectually prevented the immigration of temperate fortes of plants during the glacial epoch. This would undoubtedly be a fatal objection, were there not abundant evidence to show that Java has been formerly connected with Asia, and that the union must have occurred at about the epoch required. The most striking proof of such a junction is, that the great Mammalia of Java, the rhinoceros, the tiger, and the Banteng or wild ox, occur also in Siam and Burmah, and these would certainly not have been introduced by man. The Javanese peacock and several other birds are also common to these two countries; but, in the majority of cases, the species are distinct, though closely allied, indicating that a considerable time (required for such modification) has elapsed since the separation, while it has not been so long as to cause an entire change. Now this exactly corresponds with the time we should require since the temperate forms of plants entered Java. These are now almost distinct species, but the changed conditions under which they are now forced to exist, and the probability of some of them having since died out on the continent of India, sufficiently accounts for the Javanese species being different.
In my more special pursuits, I had very little success upon the mountain--owing, perhaps, to the excessively unpropitious weather and the shortness of my stay. At from 7,000 to 8,000 feet elevation, I obtained one of almost lovely of the small Fruit pigeons (Ptilonopus roseicollis), whose entire head and neck are of an exquisite rosy pink colour, contrasting finely with its otherwise blue plumage; and on the very summit, feeding on the ground among the strawberries that have been planted there, Iobtained a dull-coloured thrush, with the form and habits of a starling (Turdus fumidus). Insects were almost entirely absent, owing no doubt to the extreme dampness, and I did not get a single butterfly the whole trip; yet I feel sure that, during the dry season, a week's residence on this mountain would well repay the collector in every department of natural history.
After my return to Toego, I endeavoured to find another locality to collect in, and removed to a coffee-plantation some miles to the north, and tried in succession higher and lower stations on the mountain; but, I never succeeded in obtaining insects in any abundance and birds were far less plentiful than on the Megamendong Mountan. The weather now became more rainy than ever, and as the wet season seemed to have set in in earnest, Ireturned to Batavia, packed up and sent off my collections, and left by steamer on November 1st for Banca and Sumatra.