540 OLWEN M. KEES. 



The mesenterial filaments contain large gland cells the contents of 

 which are granular and take stain deeply with borax carmine. There is 

 also a number of nematocysts, some of which are very large ; these are 

 spindle-shaped and do not stain. I am unable to detect the spiral coil 

 in any of the nematocysts of this region. There are also a few nematocysts 

 scattered about. It is very difficult in this specimen to follow the mesen- 

 terial filaments, because the gonads tend to push them together into one 

 mass. I can distinguish only one lobe at the tip of each filament and 

 in most cases this is rounded. In the directive mesenteries the lobe is 

 pointed at the tip. 



There are two oesophageal grooves, one of which is better developed 

 than the other. The ectoderm is of uniform thickness along the groove ; 

 there is present a wide zone formed by the granules, as in the ectoderm 

 of the column wall. There are no nematocysts or gland cells here, 

 this ectoderm resembling that of the column wall. Beyond the groove 

 the ectoderm is deeply folded, the folds being supported by processes 

 of mesogloea. Gland cells and nematocysts are present on these folds. 



The ectoderm of the peristome (Fig. 12) possesses a large number of the 

 gland cells, also a large number of spindle-shaped bodies filled with dark 

 granules, probably empty cases of nematocysts filled with zooxanthellse. 

 The number of gland cells increases rapidly towards the entrance of the 

 mouth, and the ectoderm in this region is raised into folds supported by 

 mesogloeal processes. 



The sphincter muscle (Fig. 11) is situated along a line joining the bases 

 of the acrorhagi. It is a well circumscribed endodermal muscle and seems 

 to be very much like that of Aulactinia gelam figured by Haddon (Plate 

 XXVIII, Fig. 6). In a vertical section of the oral disk it arises from 

 the outer wall near the base of the acrorhagi. It is almost circular, and 

 the surrounding endoderm contains numerous zooxanthellse. The 

 pedicle is very short and stout, and gives rise to numerous delicate muscle 

 fibres. These are much finer and more numerous than those of A. gelam. 

 They branch frequently near their tips, but are not so arborescent as 

 those of A. gelam. In a transverse section of the tentacle cut near 

 the base (Fig. 9) the ectoderm contains numerous spindle-shaped and 

 rectangular nematocysts. The spiral coil cannot be distinguished and 

 many gland cells are present. A nerve layer at the base of the ectoderm 

 cells is broad and distinct. The mesogloea consists of a narrow layer of 

 homogeneous structure, except in some parts where it is slightly fibrous. 

 There is a distinct ectodermal muscle, processes of the mesogloea being 

 pushed out on the ectodermal side. There is no indication of an endo- 



