REPTILIAN TAPEWORMS. 15 



which the cirri in many segments were extruded in various 

 degrees of completeness. By the side of the cirrus in several 

 proglottids was an oval projection, which is clearly the slightly 

 everted or protruded vagina. Yon E,atz has described the ovary 

 of Ichthyotcenia biroi as possessing digitiform. processes. The 

 ovary of IchthyotcBnia nilotica is solid, and the two wings are not 

 frayed out into processes ; its appearance is, in fact, that of most 

 species of the genus. The vagina when not fully mature is apt 

 to be arranged, in that joart of it which runs parallel with the 

 cirrus-sac, in a sinuous line. In quite fully mature segments the 

 vagina runs in quite a straight course in this region, and is con- 

 siderably dilated, the calibre increasing as it passes back. It is 

 not easy, however, to distinguish any part of it as a receptaculum 

 seminis. But, on the other hand, it probably corresponds to the 

 " spindelformige Anschwellung " seen by von Ratz but not by 

 Schwarz in the species Ichthyotcenia biroi. After the pear-shaped 

 swelling, Avhich is quite plain in /. nilotica, the vagina dwindles 

 greatly in calibre and becomes quite a narrow tube. That this 

 dwindling occxirs rather suddenly gives an additional appearance 

 of a receptaculum seminis to the tract lying in front of it. As in 

 other species, the vagina has an adventitious sheath formed by an 

 ingrowth of the subcuticular layer. The vagina, when it reaches 

 the middle of the body, passes back in a straight line, and is a 

 little coiled in the neighbourhood of the ovaiy and before it 

 becomes connected w^th the shell-gland. The vagina lies dorsally 

 of the ovary and the uterus lies ventrally of the ovary in this 

 region. The shell-gland is large, and extends across about half 

 of the dorso-ventral diameter of the proglottid. It lies behind 

 the median junction of the two wings of the ovary. Close to it, 

 bu£ upon the ventral side of the median, is the very obvious and 

 strongly muscular " Schluckapparat." The vitelline glands form 

 the usual lateral strips. 



Before the eggs are ripe the icterus is visible as an empty cavity 

 running antero-posteriorly through the whole of the middle of 

 the segment. It is straight, with numerous closely adpressed and 

 irregular outpocketings. The appearance may also be described 

 as of a wide tube partially divided by numerous ingrowths of the 

 wall. When fully formed and containing ripe embryos the 

 utervis extends over the greater part of the segment from side to 

 side, though it does not touch the lateral vitelline glands. It has 

 an exaggeration of the same structure, the lateral diverticula 

 being prolonged. In transverse sections through ripe proglottids 

 (see text-fig. 3) it often appears as a series of more or less isolated 

 and circular cavities occupying the middle of the segment. The 

 ripe eggs lie loosely in the cavities of the uterus, generally 

 aggregated into masses. The shell of the egg is very thin and 

 unrecognisable, which distinguishes this species at once from 

 Ichthyotcenia varia, described later in the present paper. The 

 eggs of Ichthyotcenia iiilotica are also — and, perhaps, therefore — 

 distinctly smaller than those of the other species just mentioned. 



