QUEENSLAND AND THE NEW HEBRIDES. 317 



where they occur smgly near the surface of the ectoderm (PL 44. fio-. 4^ 

 nem. h). A well developed ectodermal muscle on small mesogloeal plaitino-s 

 is present. Between the ectodermal nuclei and this muscle is a clear nervous 

 zone containing numerous nerve-cells scattered irregularly, and a great number 

 of small oval highly refractive bodies which do not stain. These bodies are 

 most abundant in the tentacles especially towards the tips (PI. 44. fig. 4, r.h.), 

 but are also present in the disc. Von Heider (7) describes similar structures 

 in the disc of Z. cliiercMce. The mesogloea is thin, and contains lacunge and 

 occasional enclosed cells (PI. 44. fig. 4, m.). The endodermal muscle is 

 small and flat (PI. 44- fig. 4, end.m.). The endoderm is much thicker than 

 the ectoderm, and so crowded with zooxanthellse that the endodermal nuclei 

 are generally only visible at the edge of the lumen, which itself is very 

 small. 



Disc (PI. 44. fig. 5). — The ectoderm of the disc is broad and its structure 

 unusual. Internal to the nuclei of the columnar cells there is a granular 

 nucleated zone of considerable breadth. In the centre of the disc this zone 

 is divided by a clear space crossed by fibres, which does not exist in the 

 peripheral part of the disc. This granular ectoderm frequently invades the 

 mesogloea and reaches the endoderm. The layer of mesogloea therefore is 

 apparently not continuous through the disc, and where present is broken into 

 pieces of various shape (PI. 44. fig. 5, m.). An endodermal 'muscle is seen 

 only where mesogloea is also present. This granulated ectoderm is present 

 through the whole disc, and is at its thickest at the commencement of the 

 lip. It disappears as the lip turns over into the oesophagus. Von Heider 

 describes " eine eigenthtimliche Gewebeschicht " in the disc of Z. cliiercliice 

 (7), which is y&yj similar to this structure, but which does not invade the 

 mesogloea, and is also apparently quite distinct from the overlying ectoderm. 

 In the endoderm, which is half the width of the ectoderm, the zooxanthellse 

 present are not sufficiently numerous to conceal the endoderm cells. The lip 

 is raised. 



CEsopliagus. — The ectoderm of the oesophagus consists of three zones as 

 described in Z. flos marinus, McMurrich & Duerden (3 and 8), and in 

 Z. chiercMce, von Heider (7). Nematoc3^sts are very numerous, and o-land- 

 cells much more so than figured by von Heider (7). A sulcar groove is 

 present, and the ectoderm which lines it is thinner and smoother than 

 elsewhere. The folding of the ectoderm is very irregular. 



Mesenteries (PI. 44. fig. 6). — The mesenteries in three specimens cut 

 numbered 36, 38, and 40. Owing to great increase in numbers of zooxan- 

 thellse in the endoderm near the oesophagus, the mesenteries are much^thicker 

 there than towards the column-wall. Nematocysts are also present. The 

 mesogloea is thick, reaching its maximum in the directive mesenteries. The 

 longitudinal muscle is strongly developed on long plaitings of the mesoo-loea 

 (PI. 44. fig. 6, l.m.). The parieto-basilar muscle is well developed on both 



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