216 Transactions of the 



The principal ganglion is situated to the left of the conspicuous 

 otohthic vesicle, half the circumference of which it embraces ; 

 anteriorly it is prolonged by a continuation of the same substance, 

 which on arriving at the posterior border of the mouth divides, in a 

 fork-hke manner, into two branches, which half surround the 

 mouth between them. I did not see in these specimens the nerve 

 which Dr. Fol declares unites the two ends of these branches over 

 the haemal edge of the mouth ; the posterior end of this main 

 ganglion terminates in an enlargement, which contains a body 

 resembling a nucleus. The whole of this may be looked upon as 

 one ganglion, as the nature of the material is the same throughout. 

 Three principal nerves are given off from the posterior end of this 

 ganglion, the external one on each side supplies the branchial 

 apertui'es ; the middle nerve passes down towards the posterior end 

 of the body, first outside the pharynx and then between the cesopha- 

 gus and the stomach, and reaching a depression between the two 

 lobes of the stomach it turns towra-ds the haemal side of the body 

 and joins the first ganglion of the tail ; this ganglion is larger than 

 any of the remaining ganglia of that appendage ; it is elongated 

 and fusiform, composed of several elements, and gives off several 

 nerves to the muscles adjacent. The number of ganglia in the tail 

 varies from nine to twelve ; they are all of small size in comparison 

 to the first, containing not more than two or three elements, and in 

 some cases only one, which looks like a mere swelling of the com- 

 missural nerve. 



I noticed a curious mode of termination of the nerves in the 

 muscles of the tail in some specimens, which is also mentioned by 

 Dr. Fol ; each branch of some of these nerves, when it reaches the 

 muscle, terminates in a little swelling. Whether this swelling was 

 on the outside or the inside of the muscle I did not determine ; 

 according to Dr. Fol it was on the latter. They reminded me of 

 the terminations of the nerves in Tardigrada, as described by Dr. 

 Greet',* except that they were not prolonged along the surface of 

 the muscle. 



The organs of sense are two in number ; first, the otolithic 

 vesicle, which is a conspicuous spherical body containing one 

 otolithe ; secondly, a pyriform diverticulum situated immediately 

 in front of the last ; this is a hollow sac attached by its smaller 

 end to the chief ganglion. It is hollow, and strongly ciliated 

 within, the motion of the cilia resembling the flickering of a candle- 

 flame. Dr. Fol describes it as the organ of' smell, antl mentions 

 that it opens into the pharynx, but Vogt t did not see this aperture. 



Vascular System. — The only part of the vascular system that 

 is visible is the heart. The blood being colourless and totally 



* Max Schultze, ' Archiv. fiir Mic. Auat.,' Ertter Band, Er^tir Heft, 

 t Loc. cit. 



