MUSCLES OF THE BODY-WALL. 45 



areolar aspect, from the distribution of the granules or globules at intervals on the surface. 

 Moreover, when viewed in profile, these globules are found to be elevated above the general sur- 

 face, like a series of low pale warts. The tubes are attached to the hairs of the abdominal feet of 

 female crabs [Carcinus moenas) bearing ova, and are evidently of intrinsic importance to the species, 

 both as a protection against injury and desiccation. The very great change which ensues in the 

 appearance of preparations deprived of the cuticular layer shows how important this is in 

 giving character to the group. An interesting feature in regard to the skin of the Enopla (in 

 common with the Anopla), is the reaction which ensues on testing with litmus-paper. An acid 

 indication occurs in Amphiporus lactifloreus, Tetrastemma melanocephala, and Nemertes gracilis \, 

 amongst others, while a reaction not less distinctly alkaline is found in AmpJiiporus pulclier and 

 Nemertes Neesii. 



In regard to the chemical composition of the tubes secreted by these animals it may be 

 remarked that Professor E. Grube submitted those of Cerebratulus crassus from Cherso to Dr. 

 Lothar Meyer, who pronounced them to be formed of a substance closely allied to chitine. 

 Tubes made by various British species are not much affected by strong acetic acid, and become 

 pulpy only by prolonged action of Liquor potasses. 



The description of the tegumentary structures given by M. de Quatrefages differs materially 

 from that just noted, a discrepancy arising partly from his confounding the structure of the Enopla 

 with the Anopla, and partly from incorrect observations. His separation of the skin into two 

 layers, the exterior composed of smaller, the interior of larger cells, is not evident in Am/pliiporus. 

 Smaller cells sometimes do occur towards the ciliated surface, but the entire integument proper 

 is continuous as a single layer. The only representative of his " fibrous" coat, which is described 

 as lying within the former, is the structureless basement-layer. Max Schultze figures a small 

 portion of the skin of his Tetrastemma obscurum ) showing a series of large cells under the epidermis, 

 with a few granular bodies interspersed, but the view is diagrammatic. 



2. Muscular Structure of the Body -iv all. 



A very distinct belt of circular muscular fibres (Plate X, fig. 4, c), as in the Oligochseta, 

 occurs under the basement-layer of the cutis. The fibres are compact throughout, and less 

 bulky than the next coat, with which their filaments do not mix. The succeeding layer (d) 

 forms a powerful investment of longitudinal muscular fibres, and, in transverse section, is 

 generally somewhat crenated on the inner border, and fasciculated throughout. The inter- 

 fascicular substance is transparent and structureless, and evidently as mobile and contractile 

 as the fibres themselves. Numerous fibrous bands stretch from the inner surface in 

 connection with the various contents of the body. In common with the Anopla, the muscular 

 tissue is furnished with a delicate yet complete sarcolemma. Thus there are only two distinct 

 muscular coats of non-striated fibres around the body of the Enopla, making an essential difference 

 in this respect between them and the Anopla, to which (latter) previous observers have for the 

 most part confined their investigations. It will be observed, moreover, that in the general order 

 of their muscular layers the Enopla agree with the Oligochseta. 



Anteriorly the body-wall terminates in a rounded snout of the usual cutaneous textures, pre- 

 senting in transverse section (Plate X, fig. 1) an areolar and granular appearance, the soft 



