REPORT ON THE NEMERTEA. 19 



tinal caeca. Close to the posterior end of the body I cannot vouch for their presence ; their 

 extreme tenuity, and a fokling of the sections, preventing the transverse commissures, if 

 present, from being seen. Nor coukl I make out with certainty in the one specimen 

 available, whether the longitudinal stems themselves coalesce above the anus as they do 

 in the other Hoplonemertea, but on aj^riori grounds, I can hardly doubt their doing so. 



Anteriorly, the transverse commissures were present even in the immediate neigh- 

 bourhood of the brain, up to the point where the so-called vagus nerve branches off and 

 stretches forwards towards the oesophagus. 



Although, on the whole, they have a very regular course, and are situated at equal 

 intervals, still a few irregularities in these commissures must be noticed ; some of them 

 branching into two, others being connected with the preceding or the succeeding commis- 

 sure by a small bundle of nerve-fibres. 



The significance of this nervous arrangement will be discussed further on. 



The second characteristic to which I wish to draw attention is the presence of trans- 

 verse cgeca belonging to the proboscidian sheath. Although they are present in other 

 species of Drepanophorus, so that we are justified in looking upon their presence as one of 

 the typical generic characters, still I never found their walls so markedly developed as in 

 Drepanophorus lankesteri. Generally the walls are exceedingly thin and membranaceous 

 (e.g., Drepanophorus ruhrostriatus) ; here, however, they attract attention by the thick 

 cellular coating which immediately reveals its presence both in longitudinal and in trans- 

 verse sections. On PL X. fig. 4, the nature of this arrangement is clearly shown. Another 

 peculiar feature of these cseca of the proboscidian sheath is that I have found a few of 

 them coalescing peripherally with the one preceding or following them by means of a short 

 longitudinal extension, which allows these few successive caeca to intercommunicate not 

 only by means of the proboscidian cavity, but also by means of this distal connection. 



The muscular body-wall of this, as of most other Hoplonemertea, may be shown to 

 contain, in addition to the two layers a and /S [cf. PL XL fig. 8), certain cross fibres 

 not forming a definite layer, but arranged at angles of 45°, and visible in sections parallel 

 to the surface. • 



The openings of the longitudinal canals of the nephridia to the exterior are situated 

 ventrally, posteriorly, and at the same time terminally ; this constitutes another difi"erence 

 as compared with Drepanophorus ruhrostriatus which has been already described and 

 figured by Oudemans.^ On one side of the specimen investigated two openings of the 

 nephridial duct piercing the integument are at all events observable, although somewhat 

 more internally, before these deferent ducts have pierced the muscular body-wall, they 

 coalesce. There is a very close proximity between the anterior nephridial ramifications and 

 the lateral longitudinal blood-vessels. They do not, however, intercommunicate, nor do, 

 as was supposed by M'Intosh, the proboscidian sheath-caeca and the blood vascular system. 



' Loc. cit., pi. i. fig. X. 



