692 DE. H. CHABLTON BASTIAN ON THE ANATOMY AND PHYSIOLOGY 



individuals in width and thickness, and also in length from ^" to 1". The lateral bands 

 themselves in both these species have a kind of bUobed. structure, and the lemniscus 

 seems to be a growth from the anterior part of the ventral division of the band on the 

 left side, which extends backwards in contact with it, and gradually terminates by a 

 narrow posterior extremity. In transverse sections, though they are in close apposition, 

 the demarcation can always be detected between this body and the left lateral band, as 

 well as the existence of a tissue connecting it with the band of the oj)posite side. This 

 tissue is composed of an intermixed mass of fibres and nucleated cells, similar to those 

 existing in the deep integumental layer. This difiierence exists between the lemnisci in 

 the two species : in A. osculata it seems to be hollowed out in the greater part of its 

 extent into a flat elongated oval cavity, and the main canal runs along the free border of 

 the organ (Plate XXVI. fig. 6) distributing branches on all sides ; whilst in A. spiculigera 

 only the rudiment of a central cavity exists near the middle of the organ in the form of 

 a small somewhat fiddle-shaped cavity (Plate XXVI. figs. 14 & 16), and with the excep- 

 tion of a slight detour aroimd this, the main channel runs along its centre, distributing 

 branches freely as before. These branches* form at their extremities the finest possible 

 network of interlacing canals (Plate XXVI. fig. 7). Whether or not they ever end in 

 free extremities I was unable to determine ; they all seemed to possess distinct though 

 delicate walls, and no cilia could be detected within them. Their walls are probably 

 contractile, and in the main canal I detected the remains of some granular contents. 

 Posteriorly the central canal may be seen gradually to diminish in size, and terminate 

 almost imperceptibly at the narrow extremity of the lemniscus itself (Plate XXVI. fig. 6). 

 I now come to the last principal modification of these canals as existing in the Nema- 

 toids. When Siebold first called attention to these tubes, he stated that in Ascaris 

 dactyluris and in A. paucipara two anterior branches, as well as two posterior, existed 

 in connexion with the ventral aperture. ScHNEiDEEf also represented a similar arrange- 

 ment in Pelodytes strongyloides, Dacnitis esuriens, and Leptodera flexilis, whilst at an 

 anterior period Professor Huxley:}: had more fully described a similar distribution of 

 contractUe canals in a Nematoid from the Plaice, which he spoke of as an Oxyuris. I 

 have searched in the same fish and discovered in it an animal in all respects similar to 

 that represented by Huxley. This animal, however, I feel almost certain is not an 

 Oxyuris, but the Dacnitis esuriens^ of Dujakdin and Schneider. In all other respects 

 I am able to confirm the statements concerning it made by Huxley. The ventral aper- 

 ture is situated far back near the posterior extremity of the oesophagus ; it seems to lead 

 into a rather indistinct sacculated organ, which in its tm-n communicates (Plate XXVII. 

 fig. 11), in a manner that I was unable precisely to make out, mth the longitudinal 

 canals close to the junction of the anterior and posterior branches. These canals are 

 distinct walled tubes, which perforate and are situated in the lateral bands of the animal 



* Best revealed by immersing the organ in strong acetic acid. 



t MtJLLEE's ArcHv, 1858 and 1860. J Med. Times, 1856, vol. ii. p. 384. 



§ CtKullanus heieroehrous of Diesing, Syst. Helminth, vol. ii. p. 241. 



