REPORT ON THE NEMERTEA. 85 



The fact that the canal is single in the Schizonemertea, whereas it is double in the 

 Hoplonemertea, was known before (ix). It was also found to be confirmed in all the 

 Challenger species ; the bifurcation of the canal taking place in such a manner, that the 

 one branch passes through the distinct nerve-cells, forming the greater mass of the lobe, 

 whereas the other one immediately penetrates — more peripherally — amongst the much 

 larger glandular cells overcapping the foregoing. Carinina corresponds with the Schizo- 

 nemertea in having the canal single. 



Having considered the central fibrous substance of the brain in the Palseonemertea and 

 Schizonemertea, we have only to add that the Challenger Hoplonemertea have also con- 

 firmed the fact that here this fibrous core is less complicated, the brain-lobes being 

 at the same time more compact, the cephalic nerves very numerous. In Cerebratulus angus- 

 ticeps (PI. XIV. fig. 6) the fibrous core is very massive and conspicuous also. As to the 

 innervation of the numerous eyes, I have no new observations to record (cf. V and IX), 

 nor as to that of the proboscis, with the exception of the fact that in Drepanophorus 

 and Amphiporus I could distinguish numerous nerves springing from the brain-ring and 

 corresponding to the numerous longitudinal trunks in that organ. This point, which was 

 left in doubt by v. Kennel (XVl), is thus definitely settled. The phenomenon was parti- 

 cularly distinct in one specimen of Amphiporus moseleyi that had retained its proboscis. 

 It has only been partly figured in PI. IX. fig. 10, where only two are indicated, so as not 

 to obscure the diagrams. 



As to the innervation of the oesophagus, little need be said as far as the Schizo- 

 nemertea are concerned, the well-known strong and double vagus nerve being constantly met 

 with. Distinct nerve-branches are seen to take their course in the walls of the oesophagus 

 (PL XIV. figs. 3, 4) ; it was already noticed above (p. 79) that these may be partly 

 traced to separate branches springing independently from the nerve-plexus, whereas for 

 the other part they are ramifications of the so-called vagus. 



Nerves to the intestinal canal, very easily detected in the oesophageal region, could 

 not be traced with the same accuracy and distinctness in the post-oesophageal region of the 

 intestine, most probably owing to the extreme tenuity which these fine and delicate nerve- 

 twigs may here have obtained. It cannot be determined at present whether this portion of 

 the intestine also receives branches from the oesophageal vagus system or only directly 

 from the plexus, now that the existence of such a double method of innervation {Cerebra- 

 tulus corrugatus) has been actually demonstrated for the anterior regions of the intestine. 

 On a priori grounds, I look upon the latter arrangement as by far the most probable.^ 



The course of the vagus is somewhat modified in Drepanophorus, and perhaps in 

 Amphiporus. I find the strongest nerve-stem, connecting the brain with the oesojihagus, 

 in Drepanophorus, running forwards instead of backwards (PI. IX. fig. 10). Other smaller 



1 It should here be noticed that Kleinenherg {loc. cit., p. 114) has also failed to detect visceral nerve-branches to 

 the endodermal intestinal epithelium of the Annelid, Lopadorhynckus. 



