Miscellanea Zoologica. 533 



uterine cells, — but how far this view can be admitted, I must leave 

 to the determination of some better observer.* 



Many specimens, and several species, had been examined before 

 a trace of a nervous system could be detected, and I was ready to 

 conclude that these worms were truly acritous, when I was prevent- 

 ed falling into this error by the discovery of it in the Nemertes oc- 

 toculata. In this species the nervous system is distinct, and I have 

 been able since to see it in several others more obscurely. It con- 

 sists of a single oblong or ovate ganglion laid over and above the 

 oesophagus posterior to the heart ; and from this ganglion nervous 

 threads radiate in every direction, which are unbranched, of nearly 

 equal sizes, and soon lost in the body. (PI. XVIII. Fig. 2.) The 

 system has obviously a nearer relation to that of some of the lower 

 Molluscans than to any of the typical annelidans, a fact which, how- 

 ever, is not anomalous, for Mr Owen has made the same remark 

 in reference to some intestinal worms.t 



The circulating system appears to be complete, though very sim- 

 ple. Immediately behind the eyes there may be observed a roundish 

 spot on each side of a reddish colour, indicating the position and 

 figure of organs which are perhaps the centres of this system. 

 These organs are connected by a cross vessel ; and from their infe- 

 rior aspects a fine vessel departs which, running along each side be- 

 tween the intestine and skin, encircle the body with a continuous 

 canal of equal calibre in every portion of its long circuit. (PI. XVII. 

 Fig. 5.) It is uncertain whether these side-vessels are connected 

 by smaller transverse inosculations : I believe they are, and that 

 the pale lines which we observe to cross the body in some species, 

 at short and regular intervals, are produced by these vessels of com- 

 munication. (PI. XVII. Fig. 1.) On examining Fig. 5. another ves- 

 sel will be seen winding down the middle, along the surface of the 

 alimentary canal, in an undulating line. That it has any connec- 

 tion with the centre of circulation or lateral vessels I cannot affirm, 

 for I could neither trace its origin, nor its place of termination, nor 

 can I perceive that any vessel goes from it, but we may be allowed 



* Since this was written, farther observations have almost satisfied me that 

 the apparent differences in the formation of the coeoa in these subgenera are de- 

 pendent, in a great measure, on the state of the worm in regard to repletion, — 

 the distinct vesicle-like spaces being formed by the extension and coalescence 

 of the cceca around a space filled with ova, which would seem therefore to be 

 always exterior to the coeca. 



f Proceedings of the Zool. Soc. of London, pt. iii. p. 28 ; and Trans, of the 

 Zoological Society, i. p. 328-9. 



