68 



THE ANTHOZOA 



above, induce modifications in the process. The canal system 

 which permeates the porous theca becomes much extended, and, as 

 it extends, calcareous tissue is deposited between the network of 

 canals, so that the theca appears to be enormously thickened. 

 But the mesenteries do not share in this extension, and so the 

 edge-zone proper that is to say, the soft tissue which is external to 

 the calyx, and is supported on prolongations of the mesenteries 



4. 



FIG. XXXII. 



1. Section through a branchlet of Madrepora, sp. ? showing an axial zooid with septa, the 

 surrounding coenenchyme, and two buds, b, b'. 



2. Diagram of a longitudinal section of Madrepora durvillei, showing the perforations 

 in the stomodaeum leading into canals hollowed out in the mesenteries. M, mesentery ; 5, 

 septum ; Th, theca ; Ps, perisarc. 



8. Diagram of the various forms and conditions of the mesenteries in a zooid of Madrepora 

 durvillei. The mesenteries numbered 1, 1 ; 2, 2 ; 3, 3, and bear no filament and are simple ; the 

 remainder are modified, and bear filaments below the level of the stomodaeum. 



4. Diagram of a transverse section of a zooid 01 the same species. Ps, perisarc. 



6. Transverse section of a modified mesentery of M. durvillei, passing through two arms 

 of the stomodaeal canal. The thickened endoderm of the modified mesentery is clearly seen. 



(1 original ; the rest after Fowler.) 



becomes limited to the neighbourhood of the mouth of the calyx. 

 The rest of the coral is clothed with a coenosarc in which no traces 

 of the mesenteries are discoverable. From this coenosarc buds 

 arise which grow into zooids whose cavities are permanently con- 

 nected with the cavities of the other zooids composing the colony 

 by means of the system of canals just spoken of, as well as by 

 the canals of the coenosarc (see Fig. XXX. 1, and Fig. XXXII. 

 1, 4). It is clear that in the perforate corals the spongy tissue 



