48 MKS. LEONOKA J. WILSMORE ON SOME 



Zoanthus, but here the two portions are connected. The proximal portion 

 is much the longer, oi: compact form, of almost uniform width, and much 

 nearer the endoderm than the ectoderm. The second, or distal, expansion 

 occurs in the soft nose-like projections of the capitulum. These projections 

 vary in shape, and this portion of the sphincter varies with them, since it 

 occupies the whole width of the mesoglcjea here present, and runs into all 

 but the finest branches of the projections. The narrow strip connecting the 

 distal and proximal part of the sphincter lies in the circular depression round 

 the capitulum (PL 5. fig. 10). The muscle-cavities are closely pressed 

 together, polygonal in shape, and only broken by narrow irregular strands 

 of mesogloea passing transversely (PI. 5. fig. 11). In transverse sections 

 the sphincter shows a straight line on the endodermal, while on the ecto- 

 dermal side a large wave enters the base of each ridge of the capitulum. 



Tentacles (PL 5. figs. 10 & 12). — The tentacles are thick-walled, con- 

 taining a small lumen. The annular grooves on their surface involve the 

 ectodermal layer alone, which is very thick and has in its external border 

 a closely packed row of nematocysts placed at right angles to the surface 

 (PL 5. fig. 12). The strong ectodermal muscle is placed on long branched 

 mesoglceal processes which end in the nervous zone of the ectoderm. Sinc« 

 they are not enclosed by mesogloea on the ectodermal side, and the branches 

 do not anastomose, the fibres are not mesogloeal in position (PL 6. fig. 12). 

 The mesogloea is narrow and homogeneous, supporting a slight endodermal 

 muscle. The endoderm is deep and deeply folded. 



Disc. — The histology of the disc closely resembles that of the tentacle, 

 The ectoderm is deep with an outer border of nematocysts, and the strong 

 ectodermal muscle is placed on long branched mesogloeal processes, which 

 end in the nerve zone of the ectoderm. These mesogloeal processes branch, 

 but do not anastomose with one another, and therefore the muscle remains 

 ectodermal in position. This muscle becomes deeper towards the point of 

 junction of the perfect septa. The ectoderm of the disc is much narrower 

 than that of the tentacles, 



CEsophagus (PL 5. fig. 13). — The polyp was cut through the oesophageal 

 region transversely, the cut surface of the lower half being represented in 

 the figure. Twelve deep longitudinal grooves are present. Of these, the 

 two grooves which occupy the normal position of siphonoglyphes, i. e. which 

 lie between the points of attachment of the two ventral and the two dorsal 

 directives respectively^ are not much deeper than the other ten, but the 

 specimen is greatly contracted. There are also present, probably owing to 

 contraction, a number of very deep transverse grooves. The tissues are not 

 well enough preserved for histological purposes. The ectoderm, which is 

 deep, contains numerous gland-cells. The mesogloea, fibrous and thin in the 

 long grooves, widens immensely in the lobes between the longitudinal grooves, 

 and these contain numerous enclosed cells. The endoderm is narrow. 



