lOO 



NATURE 



{Jan. 30, 1890 



Antelope has been since named Hunters Antelope 

 {Danialis hiiJtteri) by Mr. Sclater (see Proc. Zool. Soc, 

 1879, p. 372, PI. xlii.), and mounted specimens of it may 

 be seen in the Mammal Gallery of the Natural History 

 Museum at South Kensington. 



It must not, however, be supposed that the rich 

 mammal-fauna of the Kilimanjaro district has been yet 

 entirely exhausted. We read, in Sir John Willoughby's 

 narrative, of a Duiker Antelope {Cephalophus), of a dark 

 red colour, found on the mountain, of which a specimen 

 was obtained by an American traveller. Dr. Abbott, but 

 not by the British sportsmen. On the same mountain, at 

 an elevation of about 9000 feet, Dr. Abbott also secured 

 an example of an " extraordinary animal " like a Serow 

 {i.e. Capricornis bubalina of the Himalayas), but " darker 

 in colour and shorter on the legs." There is therefore 

 ample room for future discoveries, both in this and in 

 other branches of natural history. The plateau surround- 

 ing Mount Kenia, which has yet to be explored scientific- 

 ally, would doubtless supply many other novelties. In 

 short, at the present time we know of no other field for 

 zoological discovery so promising and so easily accessible 

 as the slice of Eastern Africa recently assigned to Sir 

 William Mackinnon and his associates of the B.I.E.A. 

 Company, to which the author of the present volume has 

 given us such a useful and agreeable introduction. 



THE CORAL REEFS OF THE J A VA SEA AND 

 ITS VICINITY} 



O I ^'CE comparatively few of the naturalists who have 

 •^ sojourned in the Indian Archipelago have paid 

 special attention to the coral reefs of that region, it be- 

 comes a cause of satisfaction that Dr. C. Ph. Sluiter, of 

 Batavia, who has long been engaged in studying the 

 marine fauna of his neighbourhood, has taken up the 

 subject in earnest. In a paper on the origin of the coral 

 reefs of the Java Sea, and of Brandewijns Bay on the 

 west coast of Sumatra, and on the new coral formations 

 of Krakatab, Dr. Sluiter gives the results of his recent 

 preliminary investigations.-' This paper is excellent in 

 method, and the results of the highest importance. 



In the western half of Batavia Bay, where the depth 

 varies from 5-12 fathoms, there are numerous coral 

 reefs which occur in all stages of growth from the 

 incipient reef to the coral island begirt with a barrier- 

 reef. Being curious to learn how the corals first began 

 to grow on the muddy bottom of this bay, the author of 

 this paper soon found an explanation in the fact that the 

 stones and fragments of sunken Krakatax) pumice, which 

 lay in places on the mud, were covered with living corals. 

 Hence he concluded that in those favourable circum- 

 stances where several of the stones and pumice fragments 

 lay close together we might have the beginning of a reef. 

 A singular feature in the growth of these reefs then 

 attracted his attention. Some fourteen years ago, an 

 artesian boring was made in the small coral island of 

 Onrust in Batavia Bay, when an accumulation, 20 metres 

 thick, of coral debris, shells, and clay, was found to pass 

 downward into a firmer clay. The depth of the sea 

 around is only 11 metres, and after allowing about 2 

 metres for the height of the island. Dr. Sluiter infers that 

 the coral fragments have sunk down 7 metres into the 

 mud or clay of the sea- bottom. 



To support this view, the author gives a section of the 

 shore-reef of Brandewijns Bay, on the west coast of 

 Sumatra, the section being constructed from data sup- 

 plied by fifteen borings, none deeper than 24 metres, the 



' " Einiges fiber die Entstehung der Korallenriffe in der Javasee und 

 Branntweinsbai, und fiber neue Korallenbildung bei Krakatau." Von 

 Dr. C. Ph. Sluiter. (Batavia en Noordwijk : Ernst and Co., 1889.) 



^ Natuurkiindi^ Tijdschrift voor Nederlmdsch Indie, Band xlix. 



reef there being rather under 300 metres wide. As is 

 there shown, the volcanic formations of the steep coast- 

 border descend at a precipitous angle under the sea, so 

 that they do not form a foundation for the shore-reef. 

 This reef, the thickness of which varies greatly, being in 

 some places as much as 1 1 metres and in others only 

 half that amount, lies on " a substratum of clay or mud 

 mixed with coral debris., and forming a bed ranging from 

 2 to 7 metres in thickness." This substratum of clay and 

 coral passes down into a clay or mud, formed from the 

 decomposed andesitic rocks of the district, which may be 

 firm in some places and soft in others. The next point 

 brought out in the section is that the substratum of clay 

 and coral ddbris is thickest and deepest where the under- 

 lying clay is soft, and thinnest and nearest to the surface 

 when the clay is firm or is mixed with sand. From these 

 and allied considerations. Dr. Sluiter passes on to the 

 conclusion that the same process has taken place here 

 which occurs in the construction of dams and piers on a 

 yielding bottom, a large amount of coral materials having 

 been sunk in the mud, whilst the reef, by its own weight, 

 has prepared its own foundation. 



Having been familiar with the appearance of Krakatab 

 before the great eruption of 1883, Dr. Sluiter observed 

 some interesting changes in connection with the shore- 

 reefs of this island when he revisited it in 1888 and 1889. 

 The pumice and ashes at the time of the outbreak, accord- 

 ing to the account of Dr. Yerbeek, the historian of the 

 eruption, destroyed all life in the sea around, making the 

 sea-bottom a lifeless waste ; and under an accumulation, 

 20 metres thick, of these materials lies the old shore-reef. 

 In 1888 and 1889 the old condition of things was be- 

 ginning to re-assert itself. In one place a young shore- 

 reef, composed mostly of madrepores, had attained a 

 breadth of a metre, and living corals were brought up in 

 abundance by the dredge, attached to sunken pumice. 

 Amongst the measurements of coral growth given by the 

 author are those relating to specimens of Madrepora 

 nobilis, Dana, which had attained a length of from 2 to 

 23 decimetres in a period that could not have exceeded 

 five or six years, and was probably much less. Specimens 

 of Porites mucronata, Dana, had also in the same period 

 grown to a length of i decimetre. 



After referring briefly to the interesting Thousand 

 Islands, a linear group of small coral islands near 

 Batavia, many of which, in the southern part, affect the 

 atoll form, Dr. Sluiter sums up the results of his observa- 

 tions. A coral reef in the Java Sea commences its growtli. 

 on a muddy bottom in the form of a colony of corals 

 growing on the stones and su7iken pumice that there lie. 

 As it increases in extent and height, it secures its own 

 foundation by its weight, a large amount of coral materials 

 sinking into the mud to a depth of seven or less 

 metres. In its upward growth it presents a level top, and 

 displays no hollow or basin, a uniformity which it pre- 

 serves until a foot from the surface, when it dies in the 

 centre, and the agencies dwelt upon by Murray and 

 Agassiz then co-operate in forming an atoll or a 

 barrier-reef. Because the small coral reefs (500 metres 

 wide) of the Java Sea grow up uniformly until near the 

 surface, Dr. Sluiter places himself in partial antagonism 

 to a portion of Murray's theory. In this, however, he has 

 missed the point of the new view, according to which 

 such small reefs would either have no lagoon or else 

 possess a very shallow one. With this correction, his 

 partial confirmation of Murray's theory becomes more 

 complete. 



We hope that, with the great facilities at his disposal, 

 Dr. Sluiter will make an exhaustive examination of the 

 Thousand Islands, the varied and unusual conditions of 

 their growth rendering them particularly important as a 

 field for thoroughly investigating the problem. 



H. B. GUPPy. 



