OF THE NEMATOIDS, PAEASITIC AND FEEE. 595 



with a well-marked nucleus and granular contents. The other modifications of the lon- 

 gitudinal bands met Avith in these animals are those concerning which I had to speak in 

 the section on the tegumentary organs, as being connected with such an enormous 

 number of integumental pores. On this point, however, my views are, as before stated, 

 at variance with those held by Eberth. As pointed out by this observer, the bands in 

 connexion with these integumental pores frequently disappear in the posterior parts of 

 the body, whilst the others usually extend along the entire length of the animal. In 

 the Trichocephali but one such band seems to exist in the dorsal part of the anterior 

 thread-like portion of the body, whilst in the genus Trichosoma the greatest variety 

 prevails*. Thus in T. resectum and T. plica two equal bands of this kind exist in the 

 lateral region of the body ; in T. spirale there is a broad dorsal and a narrow ventral band, 

 and in T. aerophi/Uum just the opposite arrangement ; whilst in T. dispar two broad lateral 

 beinds as well as a narrow dorsal one are met with. In many of the Trichosomata (in accord- 

 ance with what I have myself seen in T. longicolle) Eberth represents what I believe to be 

 the integumental pores, situated over bands composed of ordinary cells. He, however, 

 describes the structure existing in the dorsal region of the Trichocephali as being com- 

 posed of an aggregation of columnar, polygonal cells f, and this accords pretty closely 

 with what little I have been able to ascertain concerning its structure. I distinctly 

 recognized that it presented a kind of loculated appearance in some thin transverse 

 sections which I succeeded in making of the anterior extremity of T. affinis, though I 

 was unable to make out its exact structure and relation to the integumental channels 

 immediately external to it. I think it quite possible that this band, as well as the other 

 forms of the longitudinal lines met with in the Nematoids, may be a development — only 

 a more specialized one — of the deep cellular layer of the integument. With regard to 

 the existence of secondary median lines in these animals, and many interesting details 

 concerning the remarkable variations in the proportionate size of the longitudinal bands 

 generally, Ebebth's valuable Monograph should be consulted. 



It has been already stated that in Strongylus tenuis and S. commutatus a simple cellular 

 condition of the lateral lines may be seen, such as is so common in the group concerning 

 which we have just been speaking, and, according to the observations of both Ebekth 

 and myself, this is the condition of things most commonly met with amongst the free 

 Nematoids. In many forms which Ebekth has well represented, the simple cellular 

 structure is most distinct. It may be seen amongst the species of the genera Enoplus, 

 Oncholaimus, Leptosomatum, Dorylaimus and many others, whilst in some the individual 

 cells cannot be made out, and a simply granular band appears to exist (Plate XXVIII. 

 figs. 34 & 35). In many genera, moreover, amongst which I may mention Bhabditis, • 

 Tylenchus, and Plectus, I have failed to recognize any trace of a lateral band. 



• Vide Eberth's Unters. uber Nemat. Taf. Adi. 



t He represents the muscular layer as covering the whole inner surface of this body in Trichocephahis dupar : 

 concerning this animal I can say nothing, though I am quite positive that such is not the case in T. affinis— 

 here the ccUular band is still an intermuscular organ. 



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