133 Mr. J. E. Gray^s Outline of an Arrangement of Stony Corals. 



stance is in almost every instance only to be derived from the 

 study of the result in the perfect coral, and not from the deve- 

 lopment of the buds of the animals themselves, I think it is 

 better to state, as Lamarck and De Blainville have done, the de- 

 scription of the coral as found in the collection, than to give a 

 theoretical account of the development of the buds, leaving one 

 to divine what kind of coral must result from the development 

 of the buds described. As was to be expected, the development 

 which appears from the study of the Polyphyllice, for example, in 

 the different stages of growth in the same specimens, does not 

 appear to agree with the theoretical development described by 

 the author ; for in the young state this coral has a single star 

 with regular rays, and looks like an attached Fungia, but is rather 

 more solid ; new mouths, indicated by smaller stars, are gradually 

 developed near the centre, the number increasing as the coral 

 increases in size, and at length the mass becomes free and as- 

 sumes the oblong shape. It appears to be one of the great de- 

 fects of this arrangement, that the stony corals which are free in 

 the adult state, as Fungia, Haliglossa and Polyphyllia, are sepa- 

 rated from the others by Pennatula and its allied genera, because 

 the author believes these corals to be internal and hence free ; 

 for we now know that these genera (which belong to two very 

 different groups) are all in their young state attached like other 

 corals. M. Ehrenberg compared these free internal corals to the 

 bones of cuttlefish, and the plant-like or external corals, as he calls 

 the other genera, to the shells of the oyster : he can only mean this 

 as a resemblance as regards their position, for neither the inter- 

 nal Fungia nor the external Cladocora are deposited or formed 

 like a shell, but merely consist of the hardening of the cellular 

 substance of the animal itself by the deposition of cretaceous 

 matter in the cavities of its cellular substance ; and the Fungia is 

 not truly internal, but placed in exactly the same situation as 

 regards the coral as the other genera, and only covered with a 

 reflexed part of the edge of the body. M. Ehrenberg divides the 

 plant or external corals into two sections, those which have many 

 and those which have twelve tentacles, but these divisions exactly 

 agree with the sections named Madrephylles and Madrepores 

 established by M. de Blainville. 



M. Ehrenberg in the paper above referred to has described 

 many new species ; they have not been figured, and unfortunately 

 his characters are not very clear and are difficult to understand, 

 so that I am not able to refer to them with certainty, more 

 especially as he places great reliance on the size of the coral 

 and on the size of the cells. Now experience has taught me 

 that both are very liable to variation even in different parts 

 of the same specimen or group. In the ^ Synopsis of the British 



