74 OLWEN M. REES. 



by picrocarmine showing two zones, the outer composed of loose conjunc- 

 tive tissue, and the internal zone of laminated tissue "). The mesogloea, 

 however, cannot be said to be in two zones, although the inner portion 

 is seen to be more fibrillar than the outer. Then endodermal cells have 

 a granular appearance owing to the presence of zooxanthellse, which are 

 very numerous near the free surface. Towards the mesoglcea the endo- 

 derm seems to become much weaker, the cells becoming spongy and 

 containing no algal cells. In fact, there is a tendency to form an endo- 

 dermal canal. The whole body wall is comparatively narrow^ and very 

 compact, with no lacunaB and no inclusions, and also no nematocysts. 

 It is to be noted that nematocysts are present in the outer portion of the 

 ectoderm of the body wall of Halcurias. The parieto-basilar muscle is 

 very much more elongated than in the Edwardsidse, and is somewhat 

 like a hart's tongue fern leaf, the midrib being very stout and giving of? 

 short much-branched lateral veins on either side. The retractor muscle 

 is pear-shaped and there are between 26 and 30 slender, much-branched 

 folds. Each muscle fold on careful examination shows a definite central 

 strand, as in the folds of Edivardsia timida, with an irregular layer of 

 tissue on either side, so that the whole fold has a similar appearance 

 to that of E. timida. The folds of Eloactis are, however, more slender 

 than those of E. timida, and the whole longitudinal retractor muscle of 

 E. mazeli resembles that of Peachia hastata. In P. hastata, however, 

 the retractor muscle is rather more elongated in section. The muscle 

 folds are numerous and more slender, and the whole is not so distinctly 

 marked off from the parieto-basilar muscle. In the region below the 

 stomatodseum the parieto-basilar muscle becomes much shorter and 

 the muscle folds are longer and less arborescent, while the distinction 

 between the parieto-basilar and the retractor muscles is more indefinite, 

 and the muscle folds become numerous and more slender. The mesentery 

 is continued at its distal end into a mass of sterile tissue, the cells of 

 which contain zooxanthellse. A very thin filament of mesogloea is con- 

 tinued through the centre of the sterile mass, and in places this filament 

 opens to form small bulbs with cells of zooxanthellse. All the mesenteries 

 give rise to this sterile tissue. This suggests that in a fertile specimen all 

 the mesenteries would behave alike and would thus give rise to twenty 

 gonads. In Halcurias also all twenty mesenteries are fertile. There is 

 one oesophageal groove as in Halcurias, but in Eloactis mazeli the groove 

 is deep and well defined ; whereas in Halcurias the siphonoglyphe is 

 said to be neither very deep nor well defined. In E. mazeli the ectoderm 

 of the siphonoglyphe consists of large elongated columnar cells containing 



