REPTILIAN TAPEWORMS. 17 



Ichthyotmnia varia, was represented by a great number of seg- 

 ments, but there was not a complete worm; so that I cannot judge 

 of the length of the species. I can say something, however, of its 

 dimensions as compared with the other species of IchthyotcBnia 

 which inhabit the genus Varanus. The longest piece measured 

 28 mm., and as this consisted of long and mature proglottids 

 only, it is certain that a complete individual would measure 

 more than 30 mm. A single proglottid, indeed, in one or two 

 cases was 4 mm. long, and thus the worm is obviously relatively 

 a large one as compared with other sjDecies that inhabit Varanus. 

 The breadth of mature proglottids was fully a millimetre, so 

 that this species of Ichthyotcenia is not at all thread-like but 

 flattened and ribbon-like : indeed, in all external characters a 

 typical member of the genus. Among the numerous fragments 

 of varying sizes and maturity was one piece which included a 

 scolex, which is, I think, probably not to be referred to the same 

 species. I shall deal with the characters of this individual, which 

 measured 34 mm., later. The pieces of the large worm were 

 investigated by sections, and also pieces were mounted entire, 

 stained and unstained, in glycerine. 



In transverse sections of mature proglottids (see text-fig. 4, 

 p. 18) the flattened chai-acter of the worm is very obvious. The 

 medullary parenchyma is much more coarsely spongy than I 

 have observed it to be in many tapeworms, and I have been 

 unable to detect a transverse layer of muscle separating the 

 medullary from the cortical layer. Moreover, the cortical layer 

 must be thin, for the coils of the vas deferens extend dorsally 

 and ventrally to just beneath the cellular subcuticular layer. 

 The latter layer is very strongly marked, as appears always to 

 be the case in this genus. The large cells are very deeply stained 

 by hgematoxylin. Between it and the cuticle is a delicate layer 

 of longitudinal fibres ; but I can find no other layer of longi- 

 tudinal muscles such as are figured by Schwarz * and Johnston f, 

 or have been described by myself in the present paper in an 

 Ichthyotcenia from Vaixonus oiiloticus. 



It would, I think, be difficult to miss such a layer in my prepa- 

 rations were it present. But while there is no definite layer of 

 muscles, there are certainly here and there large longitudinally 

 running fibres which I have observed both in transverse and 

 longitudinal sections. But they are scarce. As for the transverse 

 layer which Schwarz figures % as occupying the greater pai-t of 

 the medulla, I have only been able to notice a rather stretched 

 condition of the parenchymatous meshwork, pai'ticularly at the 

 extremes of the proglottids where there are no gonads developed. 

 There are very probably muscles in this meshwork running in a 

 transverse direction ; there certainly are such fibres running in 

 a dorso-ventral direction. I cannot, however, find thick layers 

 such as I understand Dr. Schwarz to insist upon in Ichthyotcenia 

 calmettei. Owing to the coarseness of the medullar meshwork 



* Loc. cit. Taf. i. fig. 4. f Zioc. cit. % Loc. cit. pi. iii. fig-. 10. 



Proc. Zool. Soc— 1913, l^o. II, 2 



