CEPHALIC FISSUKES. Ill 



ganglia. M. van Beneden makes a curious remark in regard to his Nemertes Quatrefagii—Viz., 

 that the " collier cesophagien" is peculiar for its red colour, which hue, he says, is less marked in 

 the other species of Nemertes. This colour, he explains, is not due, as believed for a long time, 

 to the nerve-ganglia, but to the vessels which surround them, and it can easily be understood 

 how the ganglia were confounded with the vascular trunks. Nothing akin to this has ever come 

 under my observation, and the minute anatomy of the region is adverse to the view. Prof. 

 Grube had previously made the same remark in describing Nemertes purpurea, Johnst, a species 

 which (judging from the descriptions) seems to differ very materially from Nemertes Neesii, and is 

 apparently one of the Anopla, but I have not yet seen any British representative. Prof. 

 Keferstein is scarcely accurate in affirming that the ganglia in this group are larger than those of 

 the Enopla. In his figure of the parts viewed from the dorsum (Taf. vii, fig. 1), the cephalic sacs 

 are not discriminated 



8. Cepialic Fissures. 



On each side of the head in the majority of the Anopla is situated an extensive fissure (Plate 

 XIX, fig. 1, and Plate XVIII, figs. 3, 8, 9, b), which commences as a shallow groove at the anterior 

 border of the snout, and terminates, in the form of a reddish pit, somewhat abruptly, just beyond 

 the entrance to the cephalic sac. A distinct constriction of the anterior region occurs behind the 

 fissures in Lineus gesserensis, thus marking off the cephalic boundary. There is nothing special 

 in the anatomy of these fissures, for they are formed by a simple extension of the cutaneous 

 elements superiorly and inferiorly, as represented in the transverse section (Plate XVIII, fig. 9). 

 Their entire surface is covered with very active cilia, which, as before mentioned, I have often seen 

 cease abruptly, and again begin to play vigorously. The vapour of chloroform, if applied in 

 sufficient quantity, causes them to stop entirely, but they again commence vibration on the 

 partial recovery of the animal. (Ersted and others have considered that these fissures perform a 

 respiratory function, but of this there is no sound evidence. Mr. H. Goodsir thought they 

 were the apertures of the male generative system, a supposition, as mentioned, scarcely 

 requiring refutation. Prof. Keferstein gives a very good summary of the views of previous 

 observers, but, while agreeing with none, he advances no new interpretation of these structures. 

 He concludes by criticising M. van Beneden's statements, to which he objects, but he has 

 scarcely reviewed them at sufficient length. M. van Beneden observes that the cephalic fissures 

 are furnished posteriorly with a pit leading into a ciliated funnel, and that the lateral vessels when 

 they approach the ganglia swell out into vesicles (" ils se renflent la en vesicules"), which simulate 

 the ganglia, and convey their contents to the exterior by the ciliated funnel just mentioned. 

 He considers that the central point of this apparatus lies immediately beneath the ganglia on 

 each side ; and he has seen, under compression, the pit of the lateral slit adjoin a large canal, 

 which terminates exteriorly by a sort of funnel, and this leads into a pouch behind the nerve- 

 ganglia. He did not see any vibratile movement within the vesicle ; and states his conviction 

 that this apparatus is similar to that in the Trematoda and Cestoidea. Thus, as Prof. Keferstein 

 says, he has nearly retrograded to the time of Huschke, who thought these fissures connected 

 with the lateral nerves, which he took for canals. In his enlarged figure, however, he represents 

 the position of the cephalic sacs fairly, but he has a large blood-vessel running exterior to the 



