750 J. H. ASHWOKTH. 



body-wall and finally come to lie upon the layer of circular 

 muscles. The connectives^ the course of which is indicated 

 externally by the metastomial grooves, unite in the hinder 

 portion of the third annulus (cf. fig. 19). Each gives off 

 numerous branches to the epidermis of the region through 

 which it passes ; in fact, the nerve-supply to the skin and 

 fullowiug segment is enormous — nerves pass into the raised 

 areas upon the skin aud repeatedly branch, their terminations 

 lying in close contact with the bases of the epidermal cells 

 (fig. 22). In addition to one or two nerves derived from each 

 connective, the skin of the region immediately below the 

 prostomium receives two moderately stout nerves which 

 arise from the ventral portion of each anterior cerebral lobe 

 close to the point of origin of the connective. These nerves 

 run on to the roof aud sides of the mouth, and their branches 

 may be traced a considerable distance along the pharynx. 

 They are apparently more numerous on the dorsal than on 

 the ventral region of the pharynx. In many sections the 

 nerves may be seen sending branches along the axes of the 

 buccal papilla) (fig. 22). The connective gives off a very 

 short but stout nerve to the otocyst. Ganglion-cells are 

 present in moderate number arouud the point of origin of 

 this nerve. The nerve comes into contact with the otocyst 

 at the point where the tube leads off to the exterior, aud is 

 intimately related to both structures. It provides the otocyst 

 with a sheath of nervous elements, which lies just below the 

 sensory epithelium, and also sends a small nervous sheath 

 along the tube. 



Nerve-cord. — The nerve-cord is situated within the 

 layer of circular muscles. The right and left fibrous portions 

 are sej)arated by a median vertical sheet of neuroglia. The 

 ganglion-cells are distributed along the whole length of the 

 cord, and are not aggregated into ganglia. They are 

 numerous, unipolar, pyriform, usually quite small cells with 

 deeply staining nuclei, and most of them are situated in the 

 ventro-lateral regions of the cord; but some few larger ones 

 measuring iruui 15 /i to oO /< in leugth, and having vesicular 



