184 J. E. DuERDEN — Jamaican Actiniaria : 



is delicately plaited for additional support to the endoderirial and ectodermal 

 musculature. 



The stomoda^um is oval in transverse sections, and the ectoderm is thrown into 

 about twenty very deep and regular longitudinal folds, the mesogloja also 

 following. In position the folds bear a rough approximation to the points of 

 attachment of the complete mesenteries. No indication of gonidial grooves is 

 presented, Haddon (1898, p. 468), on the other hand, found three gonidial 

 grooves in one example of C. hoplites, and one in another. 



The stomodseal ectoderm is uniformly ciliated, and the su])porting cells 

 give rise to the usual zone of brightly-staining nuclei ; several varieties of 

 nematocysts are represented, and various kinds of elongated, granular gland cells. 



I ollowing the folds of the ectoderm the mesogloea is very thick and triangular 

 in transverse section, but between the folds it becomes extremely narrow ; a weak 

 musculature occurs on both its ectodermal and endodermal surfaces. The endo- 

 derm is a broad layer, constituted largely of gland cells, some with clear contents, 

 and others which are granular and stain readily. 



The mesenteries are tetramerous and arranged in three cycles ; eight perfect 

 pairs, of which two pairs are directives, represent the first and second cycles, and 

 are about equally developed, while eight, incomplete, alternating pairs represent 

 the third. In the upper region of the stomodseum an odd member of the free 

 series may be connected with the stomodaeal-wall for some distance, and, in one 

 or two cases, remains attached for practically the whole stomoda^al extent. 

 This is especially noticeable in the region of one of the pairs of directives, as 

 compared with the lateral pairs. In one instance an odd member of two pairs 

 of the third cycle is connected with the stomodajum throughout its length, but on 

 one side it is the mesentery next the directives, while in the other it is the next 

 but one which is perfect. This latter condition is shown in PL xiii., fig. 4, where 

 the second mesentery from the left, belonging to the third order, has just ceased its 

 connexion at the termination of the stomodseum. Otherwise the regularity of 

 the mesenteries in this species is in striking contrast with the lack of symmetry 

 met with in other representatives of the genus. 



The mesogloea of the mesenteries is thick for some distance from its origin in 

 the column-wall, and on one side it then forms plaits of greater or less complication 

 (PL XV., fig. 3). These are of the same character as in CorynacUs australis. 

 The folds support the vertical retractor muscle, which also extends along the 

 whole face of the mesentery. In no case does the muscle give rise to a thickened 

 band, as in most members of the Actinise. 



Beyond the region of greatest plaiting the mesogloea narrows considerably ; 

 and here, in the proximal part of the polyps, the surface of the mesogloea of the 

 opposite face also becomes delicately plaited for the support of the oblique 



