T. B. ROSSETER ON HYMENOLEPIS FRAGILIS. 233 



The receptaculum-seminis (Fig. 1, Sec. 9, U.S., and Fig. 8) 

 lies anterior to the bursa on the ventral side. It is an oval 

 sac 1 69 mm. by 0*105 mm. Its fructifying canal descends 

 and forms a junction with the ovarian ducts, also with the 

 ducts of the shell- and yelk-glands. The shell-gland is oval 

 and the yelk-gland is elongated, the former being superimposed 

 on the latter in the middle of the proglottis between the 

 ovaries (Fig. 1, Sec. 9, S. and Y.G.). The ovaries are paired, 

 and are situated proximally and distally in the segment 

 (Sec. 9, P.O. and D.O.). 



Krabbe, in his Bidrag til Kinidskab, pp. 300-301, No. 57, 

 in the last paragraph of his description (external) of this species 

 of Avian tape- worm says : u I de bageste Led fandtes hos nogle 

 af Ormene tmiodne rundagtige dflg" To me, from this statement, 

 it is evident that Krabbe's specimens, like the majority of mine, 

 were ovarian, and not uterine specimens : that is to say, the 

 proglottides contained ovarian eggs, because he explicitly says 

 that the eggs were unripe (umodne), meaning that they had 

 not developed into the hexacanth or six-hooked brood stage. 



The ovarian egg (Figs. 9 a and 9b) when passed down the 

 ovarian duct for fertilisation is circular, and it possesses but 

 one soft albuminous envelope or membrane. When fertilisation 

 of the ovarian eggs commences, the organs of generation are 

 then gradually absorbed and obliterated, and the segment becomes 

 a common uterine sac. On rupturing an early uterine proglottis, 

 eggs were found in various stages of development or segmenta- 

 tion, and in some of the more recently impregnated eggs the 

 long tail of the spermatozoon could be detected protruding itself 

 from the egg-membranes. When the parent cell is evolved, by 

 cleavage and the development of the embryonic hooks, into the 

 hexacanth stage, it then possesses two distinct membranes, an 

 external and an internal envelope, and for a time continues to 

 be circular. But as the formative substance segmentates and 

 becomes bell-shaped, with a hollow or gastrula cavity, the outer 

 membrane of the egg then becomes ovular, and continues to be so, 

 for of this shape I find it in older or ripe uterine segments, and 

 in this form undoubtedly it is passed on to its nurse — an Ostracod 

 or a Copepod — for development into a cysticercoid. The circular 

 uterine egg has a diameter of 0*031 mm., the space between the 

 outer and inner membrane being 0*002 mm. The diameter of the 



