236 PCECILOCHJETIJS SERPENS. 



shaped papillae. The dorsal and ventral surfaces of the body, and the cirri of this region, 

 are covered with papillae, the epithelial glands opening at their ends. 



The ventral nerve-cord shows two large neural canals, and externally it has only the 

 hypoderm and cuticle. Allen describes the broad basal posterior cephalic region and the 

 three tentacle-like processes as representing the nuchal organ, the whole being covered 

 with sensory hairs. The lateral sensory organs have special ganglion-cells. 



The gills commence on the twenty-first segment and continue nearly to the posterior 

 end. The filaments are at first short, but soon become long, as long, or longer than the 

 cirri, and bright red. Two pairs occur on the posterior surface of each foot, one dorsal 

 the other ventral. 



The nephridia form short greenish-brown tubes in each segment, those in front open- 

 ing by ciliated funnels to the segment anterior to them, whilst from segment seventeen 

 backward nephridia (nephromixia, Goodrich), with large genital funnels attached, 

 occur. 



Reproduction. — The precise date at which the genital products ripen is not noted by 

 Allen, but it is probably in February and spring. They are found from the seventeenth 

 segment backward. The ova are lenticular in shape with a vesicular margin as in certain 

 Spionids, e.g. Spiophanes, and the surface has raised lines. The sperms occur in the 

 males in similar parts of the body. 



In his e Beobachtungen ' Claparede (1863) gave an account of an unknown, translucent 

 larval annelid which he had first found in 1855 at Christiansand, on the Norwegian 

 coast. It was common on the tow-nets at St. Vaast la Hougue. His earliest stage had from 

 fifteen to sixteen segments. The head dorsally showed two rounded bosses in front and a 

 collar or border behind, with long cilia, four long palpocils in front, and four eyes, the 

 anterior pair more widely separated. The first foot was largely developed, with a 

 tuft of longer bristles than the succeeding, but the nine following also had bristles, and a 

 brownish pigment-speck. The mouth formed a tranverse slit on the ventral surface, and 

 the alimentary canal was moniliform behind the first bristled segment. A thickened rim 

 and a circle of long cilia terminated the body posteriorly. 



His next stage had from eighteen to twenty-four segments, biramous feet, and a pair 

 of tentacles on the head. * When the larval annelid had attained the length of 3 mm., it 

 had from thirty to fifty segments. The blunt head had four eyes, a dorsal fold on 

 each side, and two short tentacles. The first foot was biramous and had the long glassy 

 bristles, and the succeeding feet were also biramous, a lanceolate outline characterising the 

 lobes in those after the tenth or thereabout. The dorsal provisional bristles were slender, 

 but the ventral were stouter, and marked by minute conical spikes, like certain sponge- 

 spicules. A pigment-speck between the lobes of the feet in the translucent annelid is a 

 conspicuous feature in these stages. 



In his latest stage the chief changes were the development of brownish pigment in the 

 dorsal lamellae of the feet and the occurrence of long processes like Indian clubs 

 instead of the usual lamellae on the seventh and four following feet. There was little change 

 in the head, which had its four eyes and two tentacles. In his Norwegian example the 

 first feet were close behind the head, and the oesophagus seemed to be longer, whilst in the 

 second and third feet two slender curved papillae occurred just in front of the space 



