A NEW SPECIES OF AVIAN TAPE-WORM. 153 



efferent duct of the yolk-gland, forms a junction with the efferent 

 duct of the receptaculum seminis. It is situated ventrally, and 

 is difficult to localise, being partially covered dorsally by the 

 yolk -gland and ventrally by the posterior portion of the ovaries. 

 Th ovaries in their initial stage are crescentic, the side in 

 proximity to the yolk-gland being concave. They are continuous 

 by the joining of the thin posterior horn of the ovisac ; they 

 are thus semi-duplex. The proximal ovary has a diameter of 

 0'034 mm. and the distal 0*027 mm. No trace of a uterine canal 

 is visible, and in the succeeding segment the receptaculum filled 

 with semen is seen to be attached by its efferent or sperm duct to 

 the ovisac or cuticle of what were the crescentic ovaries, but have 

 now become the unequal u-shaped uterus, as its impregnated ova 

 indicate, which also becomes equally developed in the two terminal 

 segments. If such be the case, that the ovaries fulfil the dual 

 capacity of ovary and uterus, then the yolk- and shell-gland must 

 pour their secretion together with the spermatozoa from what 

 in other cestodes is the ductus efferens of the receptaculum 

 seminis, directly into the ovaries, and that there the ova become 

 fertilised, and develop into the hexacanth or six-hooked brood. 

 This is not a postulate or conjectural theory, because the 

 impregnation and the development of the ova into the six- 

 hooked brood within the original ovisac give credence to such 

 a view, there is no oviduct or emissary pore from either ovary, 

 (Fig. 8, ? ), although admittedly I have not been able to trace 

 the presence of the emitted spermatozoa within the sac or in 

 the act of impregnation.* 



In the penultimate and ultimate segments the ripe ova or 

 six-hooked brood are contained in a v-shaped uterine sac. They 

 are elliptical, and have an equatorial diameter of 0*034 mm. and 

 polar axis 0*044 mm., and but two enveloping membranes could 

 be traced. The diameter of the embryo is 0*02 and length of 

 embryonic hooks 0*013 mm. 



Like Pagenstecher and Krabbe, I found isolated specimens 

 of egg-masses (Fig. 7) amongst the faeces of the same wild duck 



* The regrettable thing in connection with this is that in my endeavour 

 to discern the sperm by the aid of an immersion lens I accidentally 

 crushed my specimen which I had under observation for that purpose, 

 and being mounted in glycerine it readily yielded to the slight pressure 

 from the fine adjustment. 



