572 ox SOME SOUTH PACIFIC NEMERTINES COLLECTED BY DR WILLEY. 



the various organs lie is well developed, aud is traversed by uumerous dorso-ventral 

 muscle strands which are regularly arranged laterally and separate the various organs 

 which are subject to repetition (Figs. 15 and 16, in.d.v.). 



The muscles of the body wall present the characteristic arrangement of the genus, 

 and are not very strongly developed. 



The oesophagus is small. Shortly after the brain region and before the termination 

 of the cerebral organ it dilates into the mid-gut (" Magendarm ' ). The blind gut 

 commences anteriorly at the level of the second rhynchocoelom diverticulum aud extends 

 backwards to the genital region, where it joins the main gut at the junction of the 

 now somewhat attenuated raid-gut and intestine proper. The blind gut gives off lateral 

 pouches and in histological features resembles the intestine which also gives off 

 pouches along its course. The anus is terminal though slightly ventral in position. 



The proboscis is stout and is covered with papillae which are supplied by strong 

 branches from the proboscis nerves (Fig. 18). Beneath the papillated epithelium is a 

 layer of circular muscles and then a strong layer of longitudinal muscles which is 

 divided into two portions by the ring formed by the proboscis nerves and their 

 commissures. The proboscis nerves are 16 in number, which is probably a characteristic 

 of this species. 



The musculature of the proboscis sheath shews the basket-like structure characteristic 

 of the genus (cf. Hubrecht (6) p. 106 and PI. X. figs. 4 and 5, and Burger (1) 

 Fig. 1.50). 



The rhynchocoelom diverticula are very large and spacious extending round the 

 gut-pockets ventrally and with great regularit}-. The size of their communications with 

 the rhynchocoelom differs greatly, being in some cases very wide, especially towards 

 the anterior end, whilst in others they can hardly be distinguished. There is no 

 connection between neighbouring diverticula although the}" may be in contact anteriorly 

 in the pregonidial region. 



The vascular system is of the ordinary type described by Oudemans for Drepano- 

 phorus (Oudemans (9) PL I. fig. 7). 



The nervous system resembles closely that described by Biirger for D. spectabilis. 

 The dorsal and ventral commissures are of approximately the same size. A number 

 of strong nerves are given off anteriorly to supply the large eyes. The lateral nerv^es 

 -give off commissures which pass ventral to the gut. They also give off branches 

 passing dorsally, but these do not effect a junction with those of the opposite 

 side such as Hubrecht has described in the case of Drepanophorus lankesteri (Hubrecht 

 (6) p. 107). 



A fact well wnrthy of note is that the repetition of the ventral commissures in 

 this species does not correspond with the repetition of the intestinal pouches, gonads, 

 and muscle septa, in the way that Blh-ger has- figured for D. cnissus (Burger (:3) 

 Taf 17, fig. 16). 



The cerebral organ is large, being almost as bulky as the cerebral lobes. It 

 commences just behind the brain with which it is connected by a single strong nerve 

 and not by three as in D. spectabilis. The posterior glandular portion is of the same 

 length as the organ itself, being intermediate in this respect between B. spectahilis and 

 D. cerinus. The oesophageal nerves are small. 



