58 Transactions of the 



The connection between this system of vessels and the lateral 

 bands is somewhat different. Several longitudinal vessels anasto- 

 mosing at intervals surround the lateral bands, and represent the 

 dorsal and ventral trunks in this region. These are connected 

 directly with the transverse vessels. 



If the anterior extremity of the worm be removed about three- 

 quarters of an inch from the head and slit up vdth a fine pair of 

 scissors, by passing one of the blades through the pharynx ; a pre- 

 paration may be made like that represented in Fig. 7, by carefully 

 removing the pharynx. The four sets of longitudinal vessels — which, 

 together with the transverse vessels and vesicles, I shall no longer 

 hesitate to call a water vascular system — will be seen to form a plexus 

 by anastomosing with each other, which entirely surrounds the 

 pharynx. This portion of the water vascular system is destitute, 

 or almost destitute, of vesicles. The plexus terminates anteriorly 

 in a well-marked ring. The ring gives off six branches which 

 open externally one on either side of eacli lip. This ring, and the 

 vessels given off from it in front, are figured by Dr. Bastian,* and 

 described by him as nerves and a nervous ring ; in this he has pro- 

 bably been misled by Schneider's t description, although Schneider 

 has clearly described a totally different structure. 



The external openings on the Hj)s (Fig. 4 a a) are oval and 

 have a slightly raised margin. The external integument is con- 

 nected with the walls of the vessels at these points. Just within 

 the margin of each opening there appear to be several perforations, 

 generally two or three ; but as far as I can make out they all open 

 into a single duct. These have been described as papillae, and have 

 always been supposed to be sensory organs. J. H. Flogel^ has 

 described and figured precisely similar structures on the lips of 

 three different species of Oxyuris, but speaks of them as papillae 

 over the terminations of nerves. Dr. Bastian § admits that he has 

 been unable to trace any nerves into the papillae of Ascaris. 



With regard to the transverse ventral slit opening into the 

 water vascular system, which has been described again and again 

 in Nematoid worms, I can find no such opening in Ascaris ; there 

 is but one transverse ventral slit, and that is the orifice of the female 

 sexual organs. I have found no such opening in the male. 



The transverse opening described in some Nematoids seems, as 

 far as I can judge, to belong to some other system of organs. 



If a portion of either the dorsal or ventral main trunk be care- 

 fully removed, with its transverse branches and vesicles, it will be 

 found that there are numerous secondary and tertiary vesicles. 



* Dr. Bastian " On Nematoid Worms," ' Phil. Trans.,' vol. clvi., p. 54. 



t Schneider. 'Monor^a-apliie der Nematoiden,' and 'Mull. Archiv.' 1863. P. 1. 



X 'Koll. Zeiischrift fiir Zoologie,' band xix., p. 234. 



§ Loc, cit. 



