•^22 MKS. L. J. WILSMORE ON ZOANtHE/E EROM 



the pio-meiit-granules increase in the region o£ the capitulum. Proximally 

 they become scattered through the mesoffloea. 



Abundant lacunse containing nematocysts and cellular tissue form a broken 

 encircling canal situated about the middle of the mesogloea. Ectodermal 

 canals entering the mesogloea are frequent (PI. 45. fig. 15, eci.c). A weak 

 endodermal muscle is present. The zooxanthellte are many rows deep in the 

 endoderm distally, proximally they are rarer. 



In the basal contracted part or pedicel of the polyp the coelenteron is 

 represented by a series of small coelenteric canals branching in a mesogloeal 

 mass, which is continuous with the column-wall and which contains many 

 lacuna3. The structure of the pedicel is, therefore, precisely that of a 

 stolon. In elongated polyps this portion is very long, at least a quarter of the 

 total length of the polyp. 



Capitulum. — The capitulum is thrown into a few fine ridges. A cuticle 

 and subcuticle are present. The subcuticle is thinner, and nematocysts are 

 more numerous than in the column-wall. 



Sphincter muscle (PI. 45. fig. 13).— The sphincter muscle is double and 

 mesogloeal. The line of demarcation between the two portions is very deep. 

 The proximal portion consists of a large number of small irregular cavities 

 which are scattered throughout the width of the mesogloea, internal to the 

 globular lacunee. All the cavities contain free muscle-cells of large size 

 which frequently entirely fill the spaces. The distal muscle is small. Its 

 cavities may be arranged in the characteristic horseshoe-shape, or more 

 irregularly as in fig. 13. 



Tentacles. — The tentacles in three cases number respectively 50, 50, and 52. 

 Cuticle and subcuticle are absent. Small narrow unstained nematocysts are 

 present in numbers in the outer border of the ectoderm, and fewer large oval 

 ones are scattered through it. Yellow pigment-granules are more or less 

 abundant in the ectoderm of many of the tentacles, while in others there are 

 only a few granules. The mesogloea is thin and contains cells. The ectodermal 

 muscle is stronger than the endodermal, and is shghtly plaited. The endo- 

 derm is so crowded with zooxanthellse that no lumen is present. 



Disc. — The structure of the disc resembles that of the tentacles, but the 

 endoderm is thinner than the ectoderm. The latter contains patches of 

 yellowish pigment. 



CEsopliagus (PI. 45. fig. 15). — The ectoderm is not thrown into definite 

 ridges, and is generally quite smooth. 



Both nematocysts and yellow pigment are present in the non-staining 

 nervous zone. The mesoglffia and endoderm are both thin. The latter 

 contains zooxanthellse. 



Mesenteries (PL 45. figs. 14 and 15). — The mesenteries in three specimens 

 cut number 50, 50, and 52. They are of the brachycnemic type and very 

 thin towards the oesophagus. The basal canal is small oval in transverse 



