40 THE VOYAGE OF H.M.S. CHALLENGER. 



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

 polyp 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 mesoglcea which are free from adventitious accretions 

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

 the whole thickness of the soft mesoglcea, 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 JEpizoanthus 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 mesoglcea of Zoanthus exhibits. I [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 

 Zoanthus is effected. 



"The mesoglcea 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 mesoglceal 

 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 mesoglceal 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 mesoglcea 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 fibrillas. 



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

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

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

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



