40 THE VOYAGE OF H.M.S. CHALLENGER 



face of the indrawn part of the body-wall. Sections through the upper region of the 

 polj'^p yield appearances similar to those described under the preceding species, though, 

 owing to the abundant and various deposits enclosed, they are not so regular and 

 elegant. 



" In those inner parts of the mesogloea which are free from adventitious accretions 

 there lie embedded in the homogeneous matrix — 1. fine radial fibres, penetrating 

 the whole thickness of the soft mesogloea, provided here and there with nuclei ; 2. round 

 mesoglcea-cells containing a large nucleus ; 3. round or oval spaces packed with cells. 

 Hertwig, who has observed similar structures in the Epizoanthus parasiticus described 

 by him, conjectures that these oval cell-islets are produced only by indifferent preserva- 

 tion, and result from the breaking down of a system of anastomosing cords, such as 

 the mesogloea of Zoantlius exhibits. 1 [Erdmann] am inclined to regard these roundish 

 heaps of cells as primary structures, like the canals of Zoanthus, since I have been 

 able to recognise them in almost all my species of Epizoanthus, which were without 

 exception in a very good state of preservation. As to their origin I have no data ; but 

 there is no reason why they should not be referred to an ectodermal origin as well as 

 the cell-canals of Zoanthus, the derivation of which from ectoderm is indisputable ; 

 besides, many of these cell -islets clearly exhibit an elongate outline, with here and 

 there even a slight tendency to branch, by which an external approximation to 

 Z^oawi/iMS is. effected. 



"The mesogloea of the mesentery is well developed,^ and on its inner edge is 

 thickened like a club. The micromesenteries project only slightly into the interior, 

 but, like the macromesenteries, clearly present marked muscle-pennons. On these 

 mesenteries there springs on the side opposite to the muscle-pennons a mesogloeal 

 lamella, which is considerably elongated in order to carry the generative organs 

 and to form, centrally to these, the mesenterial filaments. The former are present 

 in considerable numbers ; and, being cut more or less superficially owing to the con- 

 torted course of the mesentery, may be recognised in transverse section as roundish 

 balls enveloped in a thin mesogloeal lamella, pressed against the body-wall and generally 

 filling the adjacent chamber. All the specimens which I investigated were female, the 

 generative balls consisting of a large number of ova closely appressed together, but 

 separated by a fine mesogloea lamina. 



" The body-wall is deeply drawn inwards, and conceals in this region a strongly 

 built sphincter, which has the shape described for the preceding species, but which 

 is distinguished by a greater complication in the branching of the bundles of fibrillse. 



" The stomatodasum is oval, with a clearly defined siphonoglyphe. The ensheathing 

 coenenehyme measures 1-1-3 mm. in thickness; in its interior run longitudinally 

 numerous connecting tubes. The mesogloea carries on its surface foreign deposits of 

 the same character and quantity as those on the body- wall, but the inner face, which lies 



