NEPHTHYS. 7 



edge in section being inferior. Into the straight npper edge, as well as the upper lateral 

 region, the powerful oblique muscles are inserted — separated from the nervous tissue 

 only by the tough sheath. The action of these and of the adjoining longitudinal ventral 

 muscles would not appear to support the theory of quiescence of the trunks advocated by 

 some zoologists. 



The area (Fig. 37) is subdivided by a median septum which passes from the ventral 

 fissure to the dorsal edge, though in some sections it is obscured dorsally. The broad 

 circumference of the area forms a dense plexus of fibres with intervals; whilst the 

 upper median region on each side is composed of more lax tissue (which stains 

 differently) viz. of prominent fibres — transverse or oblique in direction — with granular and 

 gelatinous intermediate substance as well as small spaces in the preparations. On each 

 side of the median line in this area are two conspicuous neural canals, the inferior the 

 larger, the next considerably less, besides a variable number of others. There are, 

 especially near the two large inferior canals, and at the outer border of the central area, 

 several deeply stained granular nerve-cells. In some sections four canals are seen 

 on each side of the middle line and in a diminishing series from below upward, in others 

 only two with various minor apertures are visible. 



To the exterior of the nerve-cords is the tough layer of limiting membrane which 

 splits into fibres at the ventral median raphe. At the outer angle ventrally is a triangular 

 area occupied by oblique fibres which slant mainly from without and below inwards. 

 It is difficult to say whether any traces of circular fibres (circular coat) exist between 

 the limiting membrane and the cuticle, though such is probable. 



Cunningham 1 (1888) observes : "In Nephthys, instead of the typical canal on the inner 

 side of each (nerve-) cord, there are two large canals, one above the other, with a smaller 

 one between them. There is also a smaller canal in the external side of each cord, and 

 still smaller ones in the substance of the cords. The nerve area here is not separated 

 from the epidermis." 



Following the hint of Savigny, Cuvier separated the genus (under the name of 

 Nephthys) from the Nereids; and soon a more complete account of the characters was 

 published by Adouin and Milne Edwards. 



The generic characters given by De Quatrefages (1865) are, briefly, those of his 

 predecessors. 



Kinberg's 2 description of the genus was : — " The two antennas and the two palpi 

 similar in form, marginal ; bristles both annular and smooth ; the two maxillse nail-like 

 and depressed." He at the same time established two new genera, viz. Aglaophamus 

 and Aglaopheme. The former, originally from Banks Strait, has also been found in 

 Europe. 3 



Ehlers (1868) grouped the various forms under the genus Nephthys thus : — (1) The 

 posterior lamella? in both divisions of the foot in all the segments long, e.g., N. cseca. 

 (2) The posterior lamella? of the inferior division in all the segments long, N. Hombergii, ■ 



1 < Q. J. Micr. So./ n.s., vol. xxviii, p. 270. 



2 ' Ofvers. K. Yet. Akad./ Fork, No. 4, p. 239, 1865. 



3 c Ann. Nat. Hist./ ser. 7, vol. v, p. 262. 



