43- 



NATURE 



[October 6, 1910 



COCOS-KEELING ATOLL.' 



n^HE author, who was for fifteen months medical 

 A officer to the cable station at Cocos-Keeling, 

 presents us with an interesting book on that atoll 

 made classical bv the researches of Darwin during 

 the voyage of the Beagle. The account of the forma- 

 tion and history of the colony is a romance vividly 

 portrayed, but the main interest of the book lies in 

 the author's observations on coral-life and on the pro- 

 cesses in operation which can shape an atoll. 



The true coral animal (Madreporaria) is a colonial 

 sea-anemone, which continually deposits under itself 

 carbonate of lime, thus raising its seat higher and 

 higher above the bottom. It sits on the surface of the 

 dried coral, such as it is commonly known to us, and 

 in no way presents the features of an .Mcyonacean, 

 such as is represented in Fig. 6 of the book. It is 



reef corals is largely due to these algae, and their 

 mode of growth is sympathetic to them in that the 

 coral skeleton is deposited so as to expose the polyps 

 to the maximum amount of light. Such appear to us 

 the ordinary views of zoologists, but our author re- 

 gards sediment as the main factor to account for the 

 variability of corals; that it is an important sub- 

 sidiary factor cannot, of course, be denied. Some 

 corals,, such as Coenopsammia, have no algae, but pig- 

 ments in granules in their cells; they, of course, are 

 unaffected by light. Yet others probably have similar 

 pigment together with algEe, but our author does not 

 follow out what should be a most profitable line of 

 research. 



The statement that corals know "no natural death," 

 does not rest on observation, and is contrary to the 

 few facts we have. No zoologist would consider the 

 rate of growth of corals slow. The observations on 



(Jur..l and Atulls. 



peculiarly unfortunate that this figure should have 

 been inserted, since the skeleton of reef corals, with 

 which the author is dealing, consists entirely of dead 

 material. It exposes the writer to the suspicion that 

 he is unacquainted with the real nature of the coral 

 skeleton, and hence largely throws doubt on his really 

 admirable observations on the growth of corals in rela- 

 tion to their environment. These are in no way scien- 

 tific, but consist of the notes of a painstaking naturalist. 

 The extraordinary variabilitv in coral skeletons is 

 well known to zoologists, and may aptly be compared 

 to the growth shown by our forest trees in different 

 environments. Reef corals, too, resemble trees in 

 that they are largely dependent for their food on 

 chlorophyll, which is present in minute algae, living 

 in their digestive cavities. The coloration of most 



> "Coral and Atolls." By F. Wood-Jones. Pp. .\xiii +-392. (London: 

 Lovell, Reeve and Co., Ltd., igio,) Price 24^. net. 



NO. 2136, VOL. 84I 



the forms of growth of corals are not convincing, since 

 our author does not appear to have examined the zooids 

 to see whether he is really dealing in any genus with 

 one or more species. He is hence not justified in 

 stating that the distribution of atoll corals " is a dis- 

 tribution of types and not of species." The observa- 

 tions on the effect of silt suggest research, such as 

 has for some years been undertaken by Wayland 

 Vaughan at the Tortugas; they are not definitive 

 enough to be of much value. Vaughan, by the way, 

 found no great difficultv in transplanting corals. 



The third part of the book deals with the Cocos- 

 Keeling atoll and its problems, concluding with 

 chapters on the formation of atolls in general. We 

 agree with the author that " it is almost impossible 

 to judge of the method of formation of any atoll not 

 actually visited and examined." The lagoon of Cocos- 

 Keeling is filling up, we are told, both by organic 



