140 



granular cells lie on the contrary in the inner half of the 

 epithelium below its layer of nuclei ; but many have definite 

 necks extending through the epithelium to the exterior. 

 While the oval-shaped nuclei of the mucous cells are situated 

 at the base of their secreted mass, the nuclei of the granular 

 cells lie in the middle, and are generally round with well- 

 defined membranes and a few granules. In the earliest state 

 the cells stain of a homogeneous yellow colour. Fine granules 

 appear in this and give rise to larger spherules or masses. 

 These become concentrated towards the outer part of the cell, 

 which then sends a process to the exterior. At the same 

 time the granules become more and more deeply stained and 

 smaller (figs. 4-8). 



The Ectoderm of the External Body Wall (fig. 4) is 

 rather more vacuolar than the same layer elsewhere and 

 slightly thinner. Granular cells are relatively rare and 

 generally appear ripe. The basal nervous layer is usually 

 •distinct, and presents the punctate arrangement ot the 

 Actiniaria. Nerve cells are here and there present. A few 

 nematocysts of the regular tentacular kind, but always much 

 smaller, occur in places. 



The ectoderm of the tentacles (fig. 5) differs only in 

 being packed with the nematocysts in batteries. Mucous 

 cells are less common than elsewhere, and granular cells 

 about as numerous as in the ectoderm of the external body- 

 wall. The nervous layer is concentrated under the batteries, 

 three or four of its nuclei being often visible in a single 

 section through the middle of a battery. No definite 

 muscles can be distinguished, but the epithelium appears 

 to give off processes which are joined to special attach- 

 ments of the structureless membrane. 



The nematocysts are the same as I found in the tentacles 

 of Cofiiopsaininia (Willey's Zoo. Results, p. 368). Each has 

 about 30 turns of the thread, which in the fully ripe body lies 

 immediately under its extern.il wall, so that it projects 

 spirall)'. The development of the thread follows the same 

 lines as in Cocuopsamuiia, the redurtion in size taking place 

 pan passu with the formation of the thread. 



The ectoderm of the peristome differs only from that of 

 the external body-wall in being less vacuolated and having 

 the nuclei still more massed together. The nervous layer 

 is always distinct, and the granular gland cells are fairly 

 common, Nematocysts are not found. 



The stomodoeal ectoderm (figs. 6 and 7) exhibits the 

 same structure as that of the peristome. It is thickened 

 over the attachments of the mesenteries (fig. 6), but between 

 these is not so thick as on the peristome. In the latter 

 position the nuclei form a broad line broken only where the 



