Haddon and Shackleton — Actinke: I. Zoanthece. 681 



foraminifera, diatoms, &c., are occasionally to be found embedded in it, and in 

 the peripheral layer of mesogloea. The latter can be very distinctly seen in this 

 species. As in Z. jukesii the cells of the ectoderm appear to have become fused, 

 and crossing strands of mesogloea can only be seen in those few places where the 

 ectodermal space is nearly empty. Anastomosing ectodermal canals, very similar 

 to those found in Z. coppingeri, run through the mesogloea and are connected with 

 the basal canals of the mesenteries near the union of the column with the 

 ccEnenchyme (PL lsii., fig. 3). The surface of the column is thrown into 

 numerous folds, which appear in cross-section as deep ectodermal bays lined with 

 cuticle. 



Sphincter muscle. — The sphincter muscle is somewhat similar to that in Z. 

 juJcesii, the upper being the longer of the two parts (PI. Lxrv., fig. 5). The cavities 

 are simpler than in Z. coppingeri, but they are not so large as in Z. jukesii. 



Disc and tentacles. — The structure of the disc and tentacles is very similar to 

 that of the preceding species. There are no nematocysts in the endoderm. 



(Esophagus. — There is a well marked oesophageal groove. 



Mesenteries. — 'Of the two specimens which we have cut transversely, one shows 

 the usual brachycnemic arrangements. In the other there are four imperfect mesen- 

 teries at the sulcular side of the oesophagus, instead of the usual pair of imperfect 

 directives. The reflected oesophageal ectoderm and the structure of the 

 mesenterial filaments can be well studied in this species. As can be seen in a 

 longitudinal section, such as that figured (PI. lxiv., fig. 5), the ectoderm of the 

 oesophagus passes continuously on to the mesentery, where it suddenly becomes 

 greatly thickened, and is thrown into transverse folds, the whole thickening 

 having a crescentic form, first curving upwards and then downwards, losing itself, 

 in the mesenterial filament. The ectoderm is reflected on botli sides of every one 

 of the perfect mesenteries, presenting in transverse section a characteristic pinnate 

 appearance (PL lsiv., fig. 6). As above mentioned, the reflected ectoderm passes 

 gradually into the mesenterial filament, the characteristic V shape of the latter 

 (PL LXIV., fig. 7) being continuous with the peripheral folds of the former. 

 The lateral elements of the mesenterial filaments gradually become shorter, so that 

 as it descends only the median portion is left. Numerous nematocysts are found 

 in this lower portion of the filament (PL lxiv., fig. 8). In this species the 

 mesenterial filaments are confined to the upper part of the column, gradually 

 disappearing about the middle of the column. As the filaments disappear the 

 mesenteries also become much narrower (appearing in transverse section to 

 shorten), projecting but a little way into the coelenteron (PL lxiii., fig. 2). Lower 

 down they again widen and project further, finally uniting in the centre at the 

 base of the polyps to form the coelenteric canals of the stolon (PL lxii., fig. 3). 

 The mesogloea of the mesenteries is well developed, especially near tlie base. 



XMANS. EOr. BUB. SOC, N.S. VOL. IV., PART XIII. 5 P 



