Mr. J. E. Gray's Outline of an Arrangement of Stony Corals. 126 



tinued cells of Moniiculai'iae ; these forms gradually pass into the 

 next form. 



On the other hand, if the animal chiefly extends its size by 

 spreading out laterally, forming a thin foliaceous expanded coral, 

 the cell of the young animal has simple rays, as is shown in the 

 young Fungia Talpa, Lam., in the British Museum; and as the ani- 

 mal expands, new mouths forming new centres are developed in 

 the disc of the star. This is the mode of growth of the Agaricicey 

 PavonincBj &c., the animals being continually expanded towards 

 the margins of the corals ; and when the cavities of the stomach, 

 separated by the septa which form the plates on the surface, are 

 sufficiently expanded (or perhaps too much expanded for the 

 food conveniently to reach them), then new mouths are opened ; 

 hence the mouths, and the stars indicating these mouths, are gene- 

 rally placed in concentric lines parallel with the edge of the corals. 

 The foliaceous corals which are thus developed are easily known 

 from those which are produced by buds, for in the latter instance 

 (as the Gemmipora) the edge of the coral is formed by the last- 

 formed buds or stars, while in these the edges are formed by the 

 extended side of the stomach, and are thin and marked above 

 with the laminae of the stomach, the stars being some distance 

 within the margin. 



In these corals the animals form a common mass, the cell of 

 the stomach of the different mouths having a more or less com- 

 plete communication with each other, which is not the case with 

 those which enlarge by buds, the polypes and their stomach 

 being separate from each other, and the animal only united by 

 their cellular integuments. 



The manner in which the buds are developed also greatly mo- 

 difies the form of the coral ; thus if they are developed from the 

 expansions of the base, the coral formed is crustiform or rounded, 

 as in some Asti^cea; and if from the upper part of the cell, then 

 the coral is generally arborescent and branched* It may be ob- 

 served that it is the marginal or terminal that is the last deve- 

 loped bud, which shows plainly the manner in which the buds are 

 developed, as the after- development of the coral obliterates the 

 separation between them ; and further, when branches of different 

 stems meet or cross they are frequently united together in a single 

 network, as is the case with the horizontally expanded Madrepores 

 and Oculina virginea, and if the branches are arranged parallel 

 and by their growth become near each other, they by the deve- 

 lopment of the animal are united into a single expanded mass, 

 as in Madrepora palmata, where the separate spike-like branches 

 which are gradually united together to form the fronds are to be 

 seen on its edges. 



As in the coral animals which enlarge by the spontaneous di- 



