STUDIES ON THE DIGENETIC TREMATODES. 439 
laureata. The transverse ducts run along the anterior 
border of the anterior testis to unite in the small median 
reservoir. This contains a small number of yolk-cells in 
which the nuclei are still present. The common yolk-duct 
passes forward to join the oviduct as already described. 
It appears to be quite erroneous to speak of the secretion 
of the yolk-glands, as so many observers have done, for as I 
have shown both in the case of Stephanophiala laureata 
and the present species, the yolk substance is the result, not 
of a process of secretion, but of a process of proliferation of 
formative cells in a manner somewhat analogous to the 
production of ovarian ova or spermatozoa. The yolk-glands 
must therefore not be regarded in the same category as the 
shell-gland and prostate-gland, which produce a true secre- 
tion. They are glands only in the same sense as the ovary 
and testes are glands. 
As in Br. palliatum, the uterus is confined to a very 
limited space between the ovary and the level of the genital 
aperture and between the intestinal diverticula on either 
side. It thus lies dorsal to the ventral sucker and occupies 
the entire thickness of the body. Its course is impossible to 
determine, owing to the greatly convoluted condition. The 
initial part, from the ootype, is lined with a highly ciliated 
membrane, but the cilia disappear after a short distance. The 
uterus then becomes distended with ova, which are surrounded 
by a countless number of sperms. ‘This condition persists 
for about a third of the total length of the uterus, and it is 
evident that we have here to deal with a true receptaculum 
seminis uterinum, which is met with in several other species 
and which performs the function of the vestigial receptaculum 
seminis proper. The condition here is evidently much 
removed from that in Br. palliatum, in which, according to 
Looss, the receptaculum seminis is full of sperms, and 
performing its true function, while no mention is made of a 
receptaculum seminis uterinum. 
The uterus terminates near the dorsal surface of the body, 
and the vagina passes almost in a straight line, dorso- 
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