142 McMURRICH. [Vol. IV. 



few and not readily distinguishable ; but in the disc they are 

 much more distinct, and form a well-marked band in sections 

 (PL VII., Fig. 6, 71). This difference in the development of the 

 nerve tract is in correlation with the development of the lon- 

 gitudinal muscles in the two regions. Occasional nuclei can 

 be distinguished in the nerve region, which are probably the 

 nuclei of ganglion cells ; they are no larger, however, than the 

 nuclei of the cells of the epithelial layer. They appear to be 

 more numerous in the disc than in the tentacles. 



The longitudinal muscles have the same development as in 

 C. mcmbranaceris. In the tentacles they cover slight elevations 

 of the mesogloea, and are arranged in a single layer ; in the 

 more contracted tentacles they appear to form two layers, the 

 fibrils of the upper layer alternating with those of the lower, 

 but they never show so extensive a development as that figured 

 by Jourdan (PL XII., Fig. 83). On the disc, however (Fig. 6, 

 Im), they are arranged on both sides of delicate lamellae of the 

 mesogloea, which are arranged "like the leaves of a book," the 

 entire muscle having a thickness of a 0.032 mm. I could find 

 in the oral tentacles no trace of the ectodermal circular muscles 

 described by Jourdan from maceration preparations. 



The mesogloea is homogeneous and destitute of cells. Its 

 ectodermal surface in the disc is raised into thin lamellae for the 

 support of the longitudinal muscle fibres. These lamellae do 

 not terminate immediately below the nervous layer, however, 

 but branch, and send branching fibres up through this layer 

 (Fig. 6, /;«.). This is very clearly seen in some of my prepara- 

 tions, especially some which were stained with eosin. One is 

 reminded by this arrangement of what R. Hertwig ('88) has 

 described as occurring in Ilyanthopsis longifilis. 



The endoderm is destitute of Zooxanthellae. Its cells give 

 rise at their bases to muscle fibres, which, as usual, are arranged 

 circularly. Occasional gland cells are seen, but I did not find 

 them so numerous as the Hertwigs figure them in C. membra- 

 naceus ; they are of one kind only, namely, the granular club- 

 shaped kind. 



(b) 77^1? Column Wall. 



The ectoderm of this portion of the body is characterized by 

 the great abundance of large nematocysts, with an irregularly 



