NA TURE 



593 



THURSDAY, OCTOBER 22, 



THE BRITISH MUSEUM CATALOGUE 



OF CORALS. 



Ca/alogue of the Madrepfirarian Corals in the British 



Museum {Natural History). \'ol. II. The Genus 



Turbinaria, the Genus Astneopora. By Henry M. 



Bernard. 410. Pp. 106 ; 33 plates. (London: 1896.) 



THE first volume of the "Catalogue of the Madre- 

 porarian Corals in the British Museum" appeared 

 in 1893 ; it consisted of a monograph of the very intricate 

 genus Mniirepora, and was the last work of the enthusi- 

 astic and talented George Brook. His lamented death 

 threatened to seriously retard the production of the 

 remaining volumes of the catalogue, for the Madreporaria 

 arc a peculiarly difficult group to classify, and as Dr. 

 Brook had by that time obtained a considerable ex- 

 perience in the classification of corals, it was expected that 

 he would have been able to bring out the succeeding 

 volumes with a reasonable degree of celerity. Dr. 

 Giinther was fortunate enough at this juncture to secure 

 the services of Mr. H. M. Bernard, who entered upon 

 his laborious duties with characteristic energy and 

 ability. 



In the volume before us Mr. Bernard describes two 

 genera which are allied to the one already catalogued. 

 In the genus Madrepora, the free-swimming larva, on 

 settling down, develops into an a.xial polyp, which gives 

 off numerous tiers of daughter polyps, any one of which 

 may become in its turn an axial polyp, giving off again 

 numerous tiers of daughters, and so on. 



In Turbinaria there is but one true axial polyp, which 

 gives off only one ring of daughter polyps ; these them- 

 selves bud, and their buds again bud, and so on. The 

 daughter polyps may perhaps be considered as axial 

 polyps which give off imperfect rings of buds, and these 

 again parts of other rings of buds. Owing to this con- 

 centric budding in a single plane, a plate is formed, on 

 the upper side of which the calicles alone occur. Accord- 

 ing to the angle at which the buds arise, so will the 

 general expanse be cup-shaped or flattened ; typically 

 the corallum is salver-shaped, but owing to irregular 

 growth the edges may become frilled, and eventually a 

 complicated foliaceous mass, with more or less erect 

 irregularly fusing fronds may result. Sometimes the 

 coralla form horizontal, dish-like growths, each fresh 

 growth covers the previous one with a larger and thicker 

 layer, there often being a space or fissure left between 

 the two growths ; or the corallum thickens enormously 

 in the centre by the lengthening of the polyps, while the 

 margin hangs down, each new growth creeping over the 

 one which preceded it. In all cases the original axial 

 polyp is submerged by subsequent growth. The down- 

 ward streaming of the ccenenchyme not only thickens 

 the stalk of the corallum, which may even be obliterated, 

 but it tends to fill up the base of the hollow of the cup ; 

 this downward streaming leaves characteristic striations. 

 Owing to the mode of growth, the Turbinarians are 

 purely ccenenchymatous corals, the epitheca has dropped 

 out of the skeleton except where it develops as a 

 secondary epitheca on the under sides of fronds, especially 

 NO. 1408, VOL. 54] 



where they tend to touch the surface upon which the 

 cord is growing. The whole corallum is built up of the 

 porous ccenenchymatous walls of the individual polyps, 

 without any trace of epithecal envelopes, or of regular 

 thecx. Hence the term Athecalia, which has been 

 proposed for such corals by Dr. Ortmann. Fifty-eight 

 species of the genus Turbinaria are described by Mr. 

 Bernard, of which some forty are new to science. 



The only account we have of the structure of the soft 

 parts of a Turbinarian is by Dr. G. H. Fowler {(Juarf. 

 Journ. Micro. Sei., xxviii. p. i). The polyps have the 

 usual two pairs of directive mesenteries ; the lateral pairs 

 of a particular polyp are not always equal in number. 

 The septa arise only between pairs of mesenteries, as 

 probably also do the tentacles. Nematocysts are evenly 

 distributed over the tentacles. Zooxanthella; are abun- 

 dant in the superficial portions of the polyps and corallum. 



In Astneopora, as in Madrepora and Turbinaria, the 

 epitheca is extremely reduced. The genus Astneopora 

 may be described as consisting typically of glomerate 

 ccenenchymatous corals, in contrast, on the one hand, with 

 Madrepora, which consists typically of branched, and on 

 the other with Turbinaria, which consists typically of 

 foliate ccenenchymatous corals. There is no definite 

 system of budding, as in the other two genera, the 

 colonies range in form from flat expanses to globular 

 masses. The septa are very feebly developed. Fourteen 

 species are known, of which nine are now described for 

 the first time. 



Mr. F. Jeffrey Bell had previously alluded {Journ. Roy. 

 Micro. Soc, 1895, p. 148) to the variations observed in 

 large masses of Turbinaria,a.nA'h\s remarks are illustrated 

 by a couple of excellent photographs. Those who have 

 attempted to identify corals will also have experienced a 

 feeling of dismay when confronted with variations in the 

 form of coralla composed of apparently similar polyps, or 

 of the vagaries of calicles on the same corallum. Often 

 has the museum naturalist anticipated Mr. Bernard's 

 question, " Is any classification of the various forms com- 

 posing a genus into separate clearly-defined species 

 possible ?" 



The following remarks by Mr. Bernard are worthy of 

 the attention of systematists in other branches of zoology, 

 and of those who interest themselves with the problems 

 of variation. 



"The only specimens which can be claimed with 

 absolute certainty as specifically identical, are a few 

 which have in each case been gathered at the same place 

 and time, and resemble one another as closely as if they 

 were two fragments of one and the same stock. Beyond 

 these no certainty exists, and strict regard to the vari- 

 ations of form and structure would compel us to label all 

 the remaining specimens as difierent species or varieties. 

 Further, I do not remember ever having seen a specimen 

 in other private or public collections which exactly re- 

 called any single specimen in the British Museum. Are 

 all these to be classed as new species .' Such a course is 

 only possible when the collection dealt with is very small ; 

 but when the number of specimens is measured by 

 hundreds, one's courage fails. Hence recourse is had to 

 a recognised but hardly satisfactory system of grouping : 

 certain striking and conspicuous specimens (or single 

 specimens which have already been described by previous 

 workers) are selected as types, and the remainder are 

 divided according as, in the opinion of the individual 



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