60 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the mesenteric cavity ; the ovaries are winding bodies containing the 

 slightly granular ova in the middle of their mesodermic layer. 



In Ihjanthus Mazeli the mesoderm contains among its delicate 

 fibres some large and very distinctly nucleated cells, giving the whole 

 the ajipearance of fibro-cartilage. 



Cerianthus memhranaceus (C. Lloydii, Gosse). — In the tentacles, 

 which carry numerous thread-cells, the mesoderm has an internal 

 circular muscular layer, a middle layer of very fine fibres, probably 

 nervous, and connecting the former with the ectoderm cells, and an 

 external longitudinal muscular layer. The tentacles of the inner 

 cycle differ from the rest, by the fact that glandular cells of peculiar 

 structure enter into the composition of the ectoderm ; their protoplasm 

 is broken up into closely packed granular matters ; some others are 

 smaller and racquet-shaped. To the muscular fibres are laterally 

 attached nucleated cells, so that they resemble the pluricellular fibres 

 noticed above. 



(Esophagus. — The ectoderm is most like that of the inner tentacles, 

 but diffars in having fewer thread-cells. 



Body-walls. — The usual three layers are to be alone distinguished. 

 The mesoderm differs from that of other Actiniaus, by having a 

 special longitudinal muscular layer, which may attain a thickness of 

 2 mm. ; the fibres become plicated during contraction. The ectoderm 

 consists of a single layer of long fusiform cells, constricted at one or 

 more points. The development of thread-cells may be traced from 

 the simple epithelial form through a racquet-shaped to an oval stage ; 

 the inferior end is lost in the granular layer, the superior forms a tube 

 leading to the exterior. The delicate fibres which traverse the granular 

 basal layer of the ectoderm in all directions are probably nervous. 

 The endoderm is exactly like that figured by Claus from Halistemma 

 tevgestinum ; the cells are long, delicate, enlarged, and ciliated at the 

 free ends ; glandular cells also occur, differing from those of other 

 Actinians, each being divided into a number of distinct portions, with 

 a common nucleus and thin cell-wall, both of which may be lost. 

 The genital lamince are formed of a median connective tissue band 

 covered on the sides by glandular and ciliated cells. In June the ova 

 and male elements are found in a fold of the median layer. The 

 male vesicles simjjly burst when mature. 



Cladocora ccesjntosa agrees with Balanophyllia regia in the characters 

 of its cellular elements. In the latter species the tentacles have the 

 fundamental characters exhibited in all the Zoantharia ; the ecto- 

 derm is densely beset with cnidocils and cilia, and below them lies a 

 dense zone of nematocysts, from whose bases long fibrillar cells run 

 inwards ; there are no glandular cells. 



The longitudinal muscular layer is thin. The mesoderm has neither 

 fibres nor nuclei. The endoderm consists of long granular cells. The 

 ectoderm of the oesophagus consists of closely packed fibrillar cells, 

 terminating in long cilia. 



Body-walls also resemble those of the Malacodermata. Among the 

 ectodermal cells of the upper part of the column are large, club- 

 shaped, usually empty, ones, probably glandular ; below these lie oval, 



