REPTILIAN TAPEWORMS. 23 



of an originally single ovum to form a number — thus lying within 

 one sheath. 



In describing the last mentioned species I have referred to a 

 scolex which probably belongs to a third species, and a further 

 examination of this and of some other fragments has convinced me 

 that this is so, and that I am right in describing these worms 

 under a different name. 



The present species is intermediate in size between the two 

 last mentioned. As already suggested, it is probably at least 

 40 mm. in length, for the largest fragment, that including the 

 scolex, is quite 34 mm. long. The head is wider than the body 

 which follows, and the greatest breadth is not attained for some 

 time ; the elongated ripe segments are about "5 mm. in width. 

 This worm is therefore much more slender than Ichthyotcenia varia. 

 The rostellar region was depressed and the four suckers look dis- 

 tinctly upwards. I ascertained that the scolex was densely beset 

 with fine spinelets as in other species. There are, of course, no 

 hooks. The neck is very short indeed, and the proglottids very 

 soon get to be as long as they are broad ; later on they become 

 about three times as long as they are broad. 



The general structure of the body when examined in transverse 

 and longitudinal sections is very like that of Ichthyotcenia varia, 

 which has just been described. The strands forming the meshwork 

 of the parenchyma are, however, much finer, and the interstitial 

 homogeneous ground substance is deeply stained, whereas a 

 corresponding immersion in the staining-fluid of pieces of 

 Ichthyotcenia varia produced no result in the way of tinging the 

 ground substance. 



The segments, however, from which I made these sections, 

 although elongated, are rather younger than those which I 

 examined (and which alone I was able to examine) in Ichthyotcenia 

 varia. The outer longitudinal muscular layer lying outside of 

 the subcuticular layer was obvious ; but, as in /. varia, I could 

 find no other definite longitudinal layer. The subcuticular cells 

 were strongly developed and very darkly stained. The water- 

 vascular tithes are two on each side and superposed, the dorsal 

 lying often fairly accurately above the ventral. 



The disproportion in calibre between the two tubes and their 

 actual size is greater than in the last species. I can find no trace 

 of transverse vessels. I could find no calcareous bodies, which are 

 present, though not abundant, in /. vctricc. The principal difference, 

 however, between the present species, which I propose to call 

 Ichthyotcenia gracilis, and /. vctria lies in the reproductive organs. 

 In the first place, the opening of the external pore is rather 

 nearer to the middle of the proglottids — sometimes, in the case of 

 shorter proglottids, actually median on the lateral margin. It is 

 never so posteriorly situated as in /. varia. I counted 80 testes 

 in one proglottid, which are more definitely arranged in this 

 species in two lateral bands, the median ai-ea being largely and 



