A NEW MAMMALIAN CESTODE. 1049 
ceased to be a pervious duct, as a narrow tract of tissue blocked 
entirely by medullary parenchyma, but still retaining a definite 
wall (text-fig. 6) separating it from the surrounding parenchyma. 
As already mentioned, the external part of the duct persists longer 
as a pervious tube ending blindly and in a dilatation. This worm, 
therefore, is interesting as showing a transition between such a 
family as the Anoplocephalidz and the Acoleide in point of its 
female efferent apparatus. 
Text-figure 6. 
a 
iatiean 
nee oo 
: 
Ny a ae 
Pee 
“> 
ca 
Monecocestus erethizontis. 
Part of a horizontal section through a proglottid a little further back than that 
referred to in text-fig. 5, to show degeneration of vagina (v.). 
r.s. Receptaculum seminis. ¢. Testes. 
The uterus of this worm is reticulate, except in very old 
proglottids in which a more complete fusion of the network tends 
to produce a saccular uterus, There are, however, even here, 
traces of the reticular condition. These may ultimately perhaps 
disappear. The uterus appears early in the body, and I have 
depicted it in young proglottids in text-figs. 7 & 8, which are re- 
spectively horizontal and transverse sections through young 
segments. A corresponding section (text-fig. 9) represents the 
mature uterus in subsequent segments. ‘This organ is seen to 
lie quite medianly in the proglottid, that is to say, it is well 
above the ovary and in the same straight line with the receptac- 
ulum seminis. The ovary has disappeared in the more mature 
proglottids. The uterus at first forms a network of rather 
delicate strands which are abundantly nucleated but contain no 
lumen, or only a very narrow one. In transverse sections the 
lumen is quite visible in young proglottids, which are, however, 
