270 J. T. CUNNINGHAM. 



Of the Nereidae I have examined Nereis virens, Sars, and 

 here cannot confirm the account of the neural canals given by 

 Mcintosh. In many sections three or four neural canals are 

 seen, which are not quite symmetrical ; these are sections 

 through inter-ganglionic transverse commissures. In the 

 cords between successive ganglia there are seen to be a single 

 pair of canals, one of which is often divided into two. The 

 pair occupy an exactly similar position to that of the neural 

 canals in Sigalion. Mcintosh states that in Nereis virens 

 there are several neural canals, viz. two large infero-lateral, a 

 single superior median and a smaller, a little below the latter 

 on each side. This apparently means five in all, two pairs and 

 one median. Probably he examined sections of the ganglia in 

 which several canals are often seen. But these have not a 

 constant relative position, and are, I believe, due to the sub- 

 division of the two canals which are seen' in the separated 

 cords. 



In Nereis pelagica I find canals placed in the positions 

 ascribed by Mcintosh to those of N. virens. There is one 

 dorsal median in the fibrous partition between the cords, a 

 pair corresponding to the typical pair of Sigalion, and another 

 pair consisting of one on the external border of each cord. 



In Nephthys, instead of the typical canal on the inner side 

 of each 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. 



In Phyllodoce no well-marked neural canals can be distin- 

 guished. The cords are widely separated from the epidermis. 



We pass now to the examination of the families of 

 Sedeutaria. 



In the Sabellidse there is a pair of canals or tubes of much 

 greater size than any seen in the Aphroditidae. Only a few 

 somites behind the head these tubes reach a thickness equal to 

 or even slightly greater than that of the nerve-cords themselves, 

 and they retain an almost uniform thickness in their course to 



