OF THE NEMATOIDS, PAEASITIC AND FEEE, 593 



(Plate XXVII. fig. 13, b, b). Just posterior to the position of the contractile sac, by means 

 of which they communicate with the exterior, they bend towards the ventral aspect of 

 the body, and the acute angle whicli the anterior and posterior branches of the same side 

 make with one another is merely due to a bend of the canal, as I have frequently seen 

 their contents pass in an oscillating manner down one limb, through the bend, and up the 

 other, in both directions. As described by Huxley, the posterior canals terminate caecally 

 close to the posterior extremity of the body (Plate XXVII. fig. 11), and I have in addi- 

 tion seen the anterior branches terminate in a similar manner opposite the middle of 

 the pharyngeal cavity. No branches seem to be given off from these canals in any 

 part of their extent ; they are of a somewhat varying calibre, the anterior branches being 

 rather broader than the posterior, and in both may be recognized a series of imperfect 

 septa extending inwards from the walls of the canals. Their contents are a clear trans- 

 parent fluid, in which a number of minute molecules are suspended ; these seem to be 

 driven backwards and forwards, partly by the movements of the animal, and partly by 

 the contraction of the canal containing them. No cilia can be detected in their inte- 

 rior. This is the only Nematoid in which I have actually seen contractions of the lateral 

 canals. The lateral bands containing them are of much the same structure as others 

 I have already described, only they often contain a seiies of nuclei, and what appear 

 to be clear spaces*. 



We have thus seen that the structure of the lateral bands is by no means always the 

 same, and that longitudinal vessels do not exist within them in all cases ; and, I must 

 say, I think it highly desirable that the descriptions of these structures as they are met 

 with in some species of the genera //e^^ra^is, Oxytcris, and Strongi/lus, given byEBEBTiif 

 and Walter;}:, should be confirmed. In Heterakis vesicularis, Ebeetii described the 

 lateral band as containing a delicate central vessel ; but if such a vessel really exists it 

 must form part of an arrangement different from any that has yet been described. I have 

 somewhat hastily examined individuals of the same species, and was quite unable to 

 detect such longitudinal vessels by any external inspection. And on account of the 

 small size of the animal I was unable to succeed, as Eberth appears to have done, in 

 making satisfactory transverse sections. Ebeeth does not seem to have recognized the 

 ventral opening and tube, which from its general appearance, and from the fact of 

 similar structures existing in an allied § animal {Heterakis acuminata), I believe to be 

 the terminations of a single or double ventral gland. Certainly it is not likely to be 



* The representation Schnkideb has given of the lateral bands in Dacnitis esuriens is I believe erroneous. 

 It seems to me that he has been misled by the appearance of the indistinct intestinal cells lining the verj- broad 

 portion of the alimentary canal in this situation. Their very light colour and almost entire freedom from 

 granular contents, was quite suggestive of cellular bodies, such as Schneidek has figured in the lateral banda 

 themselves (loc. cit. Taf. xv. fig. 8). 



t Untersuch. uber Nemat. 1863, p. 63. Idem in Wurzb. Naturwiss. Zeit. 1860, Erst. Bd. p. 41. 



t ViECHow's Archiv, 18G0. 



§ I am quite aware that the difference between these two species would warrant their being placed in dif- 

 ferent genera, but still their resemblances are such that the genera would be allied. 



MDCCCLXVL 4 Br 



