MATTHAI— RECENT COLONIAL ASTR^ID^ 53 



Polyps. (1) Tertiary couples of mesenteries sometimes complete with 12 couples, 

 often incomplete (occasionally a quaternary couple present). (2) Directive grooves not 

 deep. (3) Nematocysts I less numerous in ectoderm of oral-disc and outer wall of edge- 

 zone than in E. gemmacea, but more numerous in lower halves of stomodseal ridges and 

 in straight regions of mesenterial filaments than in that species. (4) Entocoelic pleats 

 in stomodseal region of polyp horizontal, extremely narrow, thin, comparatively few 

 and not extending to beyond the outer halves of primary mesenteries, usually restricted 

 to their outer one-third ; inner one-fifth of mesenterial mesoglsea much thickened, bearing 

 exocoelic pleats sometimes better developed than entocoelic ones. (5) Mesenterial 

 endoderra thicker on either side of inner stouter region of mesoglaea. (6) Endoderm in 

 outer wall of edge-zone as thick as the ectoderm over it, somewhat thinner in oral-disc. 

 (7) Convolutions of mesenteries scarce towards bases of polyps. 



Remarks. A. Polyps. These are oval in outline, height about 6 mm., in retraction, 

 with diameters 5 mm. and 3 "5 mm., smaller towards edges of colonies. The primary 

 mesenteries are usually attached to the sides of the septa a short distance from the 

 theca, while the remaining mesenteries are attached at the angles between walls and 

 septa. The convolutions of the mesenteries are scarce in the stomodseal region of the 

 polyp, but are protruded into the edge-zone and through the oral-disc ; they are abundant 

 below the stomodseum, becoming scarce again towards the base of the polyp. From every 

 entocoele arises a tentacle, but it has not been possible to count the exact numbers of 

 exocoelic tentacles ; the terminal batteries contain closely arranged nematocysts I, having 

 from forty to forty-five turns of the spiral, with a few II h interspersed among them. The 

 stomodeeum is oval in outline with diameters 1'75 mm. and 1mm.; one of the directive 

 grooves is often shallow ; the ridges are thicker than broad, somewhat conical in transverse 

 section, their sides sloping away, with the mesoglsea not specially thickened at their bases ; 

 nematocysts III occasionally present, in their lower halves nematocysts I frequently found 

 with fewer turns of the spiral. On the whole the stomodseum resembles in section that 

 of Favia hululensis, Gardiner. 



In the ectoderm of oral-disc and outer wall of edge-zone mucous vacuoles are 

 commonly present, nematocysts I fairly frequent, II rare. Large vacuoles are present 

 in the sub-terminal batteries as in Favia doreyensis Ed. and H. In the straight regions 

 of mesenterial filaments nematocysts I are present in small numbers, occasionally those 

 of II and III 6; in their coils large numbers of nematocysts III 6 are closely arranged 

 forming batteries, II being less numerous. In the endoderm of the outer wall of the edge- 

 zone the nuclei are arranged along its periphery, above which algae are massed together. 

 In the oral-disc the endoderm is somewhat thinner ^ and algge are less abundant ; the 

 circular layer of muscle-fibres is evident. The endoderm in the upper part of the 

 column-wall is extremely thin, in certain parts being as thin as the calicoblast with algse 

 comparatively scarce, towards the base less vacuolated, and hence less thickened than in 

 most other genera. In the tentacles it is much vacuolated being as thick as or thicker than 

 the sub-terminal batteries, with few algae as in F. lamellosa, sometimes blocking their 

 lumina. The mesenteral endoderm thickened behind the filaments as much as the 

 latter, appearing pad-like in section ; beyond this it is thin along the short non-pleatal 



