ver saw one of them； but found a totally different set of species； most of which were utterly unknown not only in Java； but also in Borneo； Sumatra； and Malacca。 For example； among the commonest birds in Lombock were white cockatoos and three species of Meliphagidae or honeysuckers； belonging to family groups which are entirely absent from the western or Indo…Malayan region of the Archipelago。 On passing to Flores and Timor the distinctness from the Javanese productions increases； and we find that these islands form a natural group； whose birds are related to those of Java and Australia； but are quite distinct from either。 Besides my own collections in Lombock and Timor； my assistant Mr。 Allen made a good collection in Flores； and these； with a few species obtained by the Dutch naturalists； enable us to form a very good idea of the natural history of this group of islands； and to derive therefrom some very interesting results。
The number of birds known from these islands up to this date is： 63 from Lombock； 86 from Flores； and 118 from Timor； and from the whole group； 188 species。 With the exception of two or three species which appear to have been derived from the Moluccas； all these birds can be traced； either directly or by close allies； to Java on the one side or to Australia on the other； although no less than 82 of them are found nowhere out of this small group of islands。 There is not； however； a single genus peculiar to the group； or even one which is largely represented in it by peculiar species； and this is a fact which indicates that the fauna is strictly derivative； and that its origin does not go back beyond one of the most recent geological epochs。 Of course there are a large number of species （such as most of the waders； many of the raptorial birds； some of the kingfishers； swallows； and a few others）； which range so widely over a large part of the Archipelago that it is impossible to trace them as having come from any one part rather than from another。 There are fifty…seven such species in my list； and besides these there are thirty…five more which； though peculiar to the Timor group； are yet allied to wide… ranging forms。 Deducting these ninety…two species； we have nearly a hundred birds left whose relations with those of other countries we will now consider。
If we first take those species which； as far as we yet know； are absolutely confined to each island； we find； in：
Lombock 4 belonging to 2 genera； of which 1 is Australian； 1 Indian。 Flores 12 〃 7 〃 5 are 〃 2 〃 Timor 42 〃 20 〃 16 are 〃 4 〃
The actual number of peculiar species in each island I do not suppose to be at all accurately determined； since the rapidly increasing numbers evidently depend upon the more extensive collections made in Timor than in Flores； and in Flores than in Lombock； but what we can depend more upon； and what is of more special interest； is the greatly increased proportion of Australian forms and decreased proportion of Indian forms； as we go from west to east。 We shall show this in a yet more striking manner by counting the number of species identical with those of Java and Australia respectively in each island； thus： In Lombock。 In Flores。 In Timor。 Javan birds 。 。 。 。 33 23 11 Australian birds 。 。 4 5 10
Here we see plainly the course of the migration which has been going on for hundreds or thousands of years； and is still going on at the present day。 Birds entering from Java are most numerous in the island nearest Java； each strait of the sea to be crossed to reach another island offers an obstacle； and thus a smaller number get over to the next island。 ＇The names of all the birds inhabiting these islands are to be found in the 〃Proceedings of the Zoological Society of London〃 for the year 1863。＇ It will be observed that the number of birds that appear to have entered from Australia is much less than those which have come from Java； and we may at first sight suppose that this is due to the wide sea that separates Australia from Timor。 But this would be a hasty and； as we shall soon see； an unwarranted supposition。 Besides these birds identical with species inhabiting Java and Australia； there are a considerable number of others very closely allied to species peculiar to those countries； and we must take these also into account before we form any conclusion on the matter。 It will be as well to combine these with the former table thus：
In Lombock。 In Flores。 In Timor。 Javan birds 。 。 。 。 。 。 。 。 。 。 。33 23 11 Closely allied to Javan birds 。 。 1 5 6 Total 。 。 。 。 。 。 。 。 。 。 。 。 。 。 34 28 17
Australian birds 。 。 。 。 。 。 。 。 。 4 5 10 Closely allied to Australian birds 3 9 26 Total 。 。 。 。 。 。 。 。 。 。 。 。 。 。 7 14 36
We now see that the total number of birds which seem to have been derived from Java and Australia is very nearly equal； but there is this remarkable difference between the two series： that whereas the larger proportion by far of the Java set are identical with those still inhabiting that country； an almost equally large proportion of the Australian set are distinct； though often very closely allied species。 It is to be observed also； that these representative or allied species diminish in number as they recede from Australia； while they increase in number as they recede from Java。 There are two reasons for this； one being that the islands decrease rapidly in size from Timor to Lombock； and can therefore support a decreasing number of species； the other and the more important is； that the distance of Australia from Timor cuts off the supply of fresh immigrants； and has thus allowed variation to have full play； while the vicinity of Lombock to Bali and Java has allowed a continual influx of fresh individuals which； by crossing with the earlier immigrants； has checked variation。
To simplify our view of the derivative origin of the birds of these islands let us treat them as a whole； and thus perhaps render more intelligible their respective relations to Java and Australia。
The Timor group of islands contains：
Javan birds 。 。 。 。 。 。 。 36 Australian birds 。 。 。 13 Closely allied species 。 。 11 Closely allied species 。 。 35 Derived from Java 。 。 。 。 47 Derived from Australia 。 。 。 48
We have here a wonderful agreement in the number of birds belonging to Australian and Javanese groups； but they are divided in exactly a reverse manner； three…fourths of the Javan birds being identical species and one…fourth representatives； while only one…fourth of the Australian forms are identical and three…fourths representatives。 This is the most important fact which we can elicit from a study of the birds of these islands； since it gives us a very complete clue to much of their past history。
Change of species is a slow processon that we are all agreed； though we may differ about how it has taken place。 The fact that the Australian species in these islands have mostly changed； while the Javan species have almost all remained unchanged； would therefore indicate that the district was first peopled from Australia。 But； for this to have been the case； the physical conditions must have been very different from what they are now。 Nearly three hundred miles of open sea now separate Australia from Timor； which island is connected with Java by a chain of broken land divided by straits which are nowhere more than about twenty miles wide。 Evidently there are now great facilities for the natural productions of Java to spread over and occupy the whole of these islands； while those of Australia would find very great difficulty in getting across。 To account for the present state of things； we should naturally suppose that Australia was once much more closely connected with Timor than it is at present； and that this was the case is rendered highly probable by the fact of a submarine bank extending along all the north and west coast of Australia； and at one place approaching within twenty miles of the coast of Timor。 This indicates a recent subsidence of North Australia； which probably once extended as far as the edge of this bank； between which and Timor there is an unfathomed depth of ocean。
I do not think that Timor was ever actually connected with Australia； because such a large number of very abundant and characteristic groups of Australian birds are quite absent； and not a single Australian mammal has entered Timor which would certainly not have been the case had the lands been actually united。 Such groups as the bower birds （Ptilonorhynchus）； the black and red cockatoos （Calyptorhynchus）； the blue wrens （Malurus）； the crowshrikes （Cracticus）； the Australian shrikes （Falcunculus and Colluricincla）； and many others； which abound all over Australia； would certainly have spread into Timor if it had been united to that country； or even if for any long time it had approached nearer to it than twenty miles。 Neither do any of the most characteristic groups of Australian insects occur in Timor； so that everything combines to indicate that a strait of the sea has always separated it from Australia； but that at one period this strait was reduced to a width of about twenty miles。
But at the time when this narrowing of the sea took place in one direction； there must have been a greater separation at the other end of the chain； or we should find more equality in the numbers of identical and representative species derived from each extremity。 It is true that the widening of the strait at the Australian end by subsidence； would； by putting a stop to immigration and intercrossing of individuals from the mother country； have allowed full scope to the causes which have led to the modification of the species； while the continued stream of immigrants from Java； would； by continual intercrossing； check such modification。 This view will not； however； explain all the facts； for the character of the fauna of the Timorese group is indicated as well by the forms which are absent from it as by those which it contains； and is b