Probable Derivation of the Mammals of Celebes.—It is clear that we have here a group of extremely peculiar, and, in all probability, very ancient forms, which have been preserved to us by isolation in Celebes, just as the monotremes and marsupials have been preserved in Australia, and so many of the lemurs and Insectivora in Madagascar. And this compels us to look upon the existing island as a fragment of some ancient land, once perhaps forming part of the great northern continent, but separated from it far earlier than Borneo, Sumatra, and Java. The exceeding scantiness of the mammalian fauna, however, remains to be accounted for. We have seen that Formosa, a much smaller island, contains more than twice as many species; and we may be sure that at the time when such animals as apes and buffaloes existed, the Asiatic continent swarmed with varied forms of mammals to quite as great an extent as Borneo does now. If the portion of separated land had been anything like as large as Celebes now is, it would certainly have preserved a far more abundant and varied fauna. To explain the facts we have the choice of two theories:—either that the original island has since its separation been greatly reduced by submersion, so as to lead to the extinction of most of the higher land animals; or, that it originally formed part of an independent land stretching eastward, and was only united with the Asiatic continent for a short period, or perhaps even never united at all, but so connected by intervening islands separated by narrow straits that a few mammals might find their way across. The latter supposition appears best to explain the facts. The three animals in question are such as might readily pass over narrow straits from island to island; and we are thus better enabled to understand the complete absence of the arboreal monkeys, of the Insectivora, and of the very numerous and varied Carnivora and Rodents of Borneo, all of which except the squirrels are entirely unrepresented in Celebes by any peculiar and ancient forms.
The question at issue can only be finally determined by geological investigations. If Celebes has once formed part of Asia, and participated in its rich mammalian fauna, which has been since destroyed by submergence, then some
remains of this fauna must certainly be preserved in caves or late Tertiary deposits, and proofs of the submergence itself will be found when sought for. If, on the other hand, the existing animals fairly represent those which have ever reached the island, then no such remains will be discovered, and there need be no evidence of any great and extensive subsidence in late Tertiary times.
Birds of Celebes.—Having thus clearly placed before us the problem presented by the mammalian fauna of Celebes, we may proceed to see what additional evidence is afforded by the birds and any other groups of which we have sufficient information. About 164 species of true land-birds are now known to inhabit the island of Celebes itself. Considerably more than half of these (ninety-four species) are peculiar to it; twenty-nine are found also in Borneo and the other Malay Islands, to which they specially belong; while sixteen are common to the Moluccas or other islands of the Australian region; the remainder being species of wide range and not characteristic of either division of the Archipelago. We have here a large preponderance of western over eastern species of birds inhabiting Celebes, though not to quite so great an extent as in the mammalia; and the inference to be drawn from this fact is, simply, that more birds have migrated from Borneo than from the Moluccas—which is exactly what we might expect both from the greater extent of the coast of Borneo opposite that of Celebes, and also from the much greater richness in species of the Bornean than the Moluccan bird-fauna.
It is, however, to the relations of the peculiar species of Celebesian birds that we must turn, in order to ascertain the origin of the fauna in past times; and we must look to the source of the generic types which they represent to give us this information. The ninety-four peculiar species above noted belong to about sixty-six genera, of which about twenty-three are common to the whole Archipelago, and have therefore little significance. Of the remainder, twelve are altogether peculiar to Celebes; twenty-one are Malayan, but not Moluccan or Australian; while ten are Moluccan or Australian, but not Malayan. This
proportion does not differ much from that afforded by the non-peculiar species; and it teaches us that, for a considerable period, Celebes has been receiving immigrants from all sides, many of which have had time to become modified into distinct representative species. These evidently belong to the period during which Borneo on the one side, and the Moluccas on the other, have occupied very much the same relative position as now. There remain the twelve peculiar Celebesian genera, to which we must look for some further clue as to the origin of the older portion of the fauna; and as these are especially interesting we must examine them somewhat closely.
Bird-types Peculiar to Celebes.—First we have Artamides, one of the Campephaginæ or caterpillar-shrikes—a not very well-marked genus, and which may have been derived, either from the Malayan or the Moluccan side of the Archipelago. Two peculiar genera of kingfishers—Monachalcyon and Cittura—seem allied, the former to the widespread Todiramphus and to the Caridonax of Lombok, the latter to the Australian Melidora. Another kingfisher, Ceycopsis, combines the characters of the Malayan Ceyx and the African Ispidina, and thus forms an example of an ancient generalised form analogous to what occurs among the mammalia. Streptocitta is a peculiar form allied to the magpies; while Basilornis (found also in Ceram), Enodes, and Scissirostrum, are very peculiar starlings, the latter altogether unlike any other bird, and perhaps forming a distinct sub-family. Meropogon is a peculiar bee-eater, allied to the Malayan Nyctiornis; Rhamphococyx is a modification of Phænicophaes, a Malayan genus of cuckoos; Prioniturus (found also in the Philippines) is a genus of parrots distinguished by raquet-formed tail feathers, altogether unique in the order; while Megacephalon is a remarkable and very isolated form of the Australian Megapodiidæ, or mound-builders.
Omitting those whose affinity may be pretty clearly traced to groups still inhabiting the islands of the western or the eastern half of the Archipelago, we find four birds which have no near allies at all, but appear to be either ancestral forms, or extreme modifications, of Asiatic or
African birds—Basilornis, Enodes, Scissirostrum, Ceycopsis. These may fairly be associated with the baboon-ape, anoa, and babirusa, as indicating extreme antiquity and some communication with the Asiatic continent at a period when the forms of life and their geographical distribution differed considerably from what they are at the present time.