OF THE NEMATOIDS, PABASITIC AND FEEE. 591 



Filaria piscium Siebold* described "un organe rubaniforme cache dans la cavite du 

 corps, parcouru par des canaux formant un reseau, ct qui rappelle les lemnisques des 

 Acanthocephales." He also stated that he had met with a similar organ in A. oscnlata. 

 ScHNEiDEB coniirmsf Siebold's account of the existence of this organ in a species of 

 Filaria piscium, and discovered that the main canal traversing it leaves this body to open 

 externally. He is uncertain whether to look upon it as a special organ, or as a part of 

 the ordinary water-vascular system, and states moreover that the lateral band of the left 

 side appeared to be wanting in the animals he had examined. It must be home in 

 mind that under this same name of Filaria jnsdujn several different species are probably 

 included. I do not know from what animal the immature Nematoids examined by 

 Siebold and Schneidee were taken. In all likelihood they were not from the Haddock, 

 since in animals removed from beneath the peritoneal membrane of this fish I have 

 found a different structure prevailing. In them, both lateral bands were present and of 

 the same size (Plate XXII. figs. 6 & 8), though only the one of the left side possessed an 

 axial canal. This canal could be seen most distinctly when the entire animal was 

 examined. It was provided with distinct walls having an appearance of internal septa 

 at intervals (Plate XXII. fig. 7), pursued an undulating course, terminating apparently 

 near the extremity of the body in a caecal ending, and left the lateral band anteriorly 

 to open in the mid-ventral region opposite the termination of the anterior third of the 

 oesophagus. Nothing corresponding to a lemniscus could be detected, and no vessel seemed 

 to be given off from this main canal in any part of its extent. This arrangement is very 

 interesting, inasmuch as it may be considered directly intermediate between what has 

 been already described as existing in A. lumhricoides, «&c., and what I have met with in A. 

 osculata and A spiculigeraX. In both these latter animals I have found a canal on the 

 left side of the body only, which leaves the substance of the lateral band, far forwards, to 

 gain the ventral region, where it appears to open at the anterior extremity of the body 

 between the two lower head lobes. In both it gives off numerous branches in the sub- 

 stance of the left lateral band, and ramifies still more minutely in a pecuhar, elongated 

 development from this structure existmg in the anterior part of the body (Plate XXVI. 

 figs. 6 & 7). This prolongation constitutes the so-called " lemniscus" of Siebold. The 

 ramifications of tlie canal are confined to this lemniscus, and to the portion of the lateral 

 band anterior to it; so that no vessels or canals can be found on either side in the 

 lateral bands of the posterior half of the body. In both animals the lemnisci present 

 a somewhat similar appearance ; they are elongated structures lying by the side of the 

 left lateral band, deeper in tint than it and of a light brownish hue, varying in different 



* 'WrEBMANN, Archiv, 1838, i. p. 310. Idem in Man. d'Anat. Comp. 1850, vol. i. p. 135. 



t MtJixEB's Archiv, 1858. 



J I was induced to examine this latter animal on account of a peculiar structure stated to exist in it by 

 DuJAKDHf, which he descrihed in these words : " Clotson s<!parant I'intestin de I'uterus, et forme'e par un 

 cordon jaune glanduleux ^pais, que des membranes blanches unissent aux deux cordons lateraux" (Hist. Nat. 

 des Helminth, p. 206). The only body at all answering to this description is what I am now about to describe. 



