168 ON OPHIDIAN TAPEWORMS. 



parenchyma. The number of fibres in a single vertical row was 

 about 12 ; and they were not associated into bundles. The 

 individual fibres were, indeed, rather far apart. The section 

 illustrating the structure of this region of the body is represented 

 in text-fig. 37, and it also shows that the medullary region is 

 to a slight extent invaded by these longitudinal fibres. It will 

 be observed that we can detect in this species of Ichthyotcenia an 

 arrangement of the muscular system like that of the Ichthyo- 

 tseniids of Vciranus, which I follow v. Linstow in assigning to a 

 separate genus Acanthotcenia *. The resemblance, however, is 

 not exact ; for in Acanthotoinia the fibres are associated into 

 definite bundles, which is as definitely not the case in the present 

 species. Still there is a likeness which so far weakens the case 

 for the generic distinctness of Acantkotcmiia. And, furthermore, 

 I can find in the Ichthyotmnia under consideration no marked 

 layer of longitudinal fibres in the body generally, such as is 

 obvious, for example, in Ophidotcenia russelli described above. 

 Indeed, Schwarz, remarks that " die innere Langsmuskulatur ist 

 schwach." I do not assert that there may not be some delicate 

 fibres here ; but there is nothing so conspicuous as is to be met 

 with in many other forms. The musculature therefore in this 

 region of the body agrees with that of Acanthotoinia ; but there is 

 no spiny covering of the scolex. Schwarz has remarked upon the 

 presence in /. mai'enzelleri, as well as in /. calmettei, of transverse 

 muscular fibres occupying the whole of the medullary layer. 

 I cannot interpret the appearance of the transverse sections of 

 the present species in that fashion. 



The accompanying drawings (text-fig. 38, p. 167) show two 

 sections of this species, of which the upper one is from a region 

 of the body anterior to the lower one. It will be seen that in 

 both the medullary parenchyma differs from that of Ichthyotcenia 

 gabonica figured above f by the more strongly marked fibrous 

 looking network in the meshes of which the homogeneous ground 

 substance lies. Furthermore, it seemed to me that this network 

 was considerably more emphasized in the posterior region of the 

 body than in the more anterior segments. In the posterior 

 region, moreover, I did not always detect the water-vascular 

 tubes, which are quite easy to see more anteriorly as is to be 

 gathered from an inspection of the figure to which I have referred. 

 The difficulty of seeing these tubes is further evidence of the 

 greater thickness of the network in the more posteiiorly situated 

 proglottids. Whether muscular fibres lie in this network I have 

 not been able to see ; but I am of opinion that the network is 

 not a transverse muscular layer, but merely an exaggeration of 

 the network which is always visible in this situation in these and 

 other tapeworms, and in which may lie musciilar fibres inde- 

 pendent from it. I have already directed attention to the 

 presence of such muscular fibres in Ichthyotcenia gabonica 

 described above. 



* P. Z.S. 1913, p. 5. t Supra, p. 155, text-fig. 33. 



