DISPOSITION of THE GENITAL PASSAGES. 



709 



tribution of these yellow ducts is not exclusively confined to the 

 joint to which they properly belong, but they extend beyond it into 

 the anterior portion of the joint behind. What we have already 

 emphasised in regard to the vasa efferentia is thus true also of these 

 yolk-ducts — a new proof of the correctness of the assertion that in 

 Bothriocephalus the individualism of the joints is much less perfect 

 .than in Tcenia. 



The disposition of the efferent ducts on the dorsal surface is much 

 more difficult to follow than on the ventral, yet it seems probable 

 that they are everywhere confined to the cortical layer, and that the 

 ramifications of the yellow ducts never traverse the central layer, but 

 extend along the sides, and in this way pass from ventral to dorsal 

 surface. The only portion of the apparatus which seems to sink 

 into the layer is the unpaired collecting tube, 

 which arises from the union of the yellow 

 ducts at the point whence they radiate out- 

 wards, and then extends inwards, penetrating 

 the muscle-layers and opening close in front 

 of the coiled gland (Fig. 371) into the fertilis- 

 ing canal. 



It is in this way possible that, along with 

 the (fertilised) ova, yolk-cells also pass into 

 the terminal portion of the uterus, and that 

 both kinds of elements become enclosed in a 

 common shell. The material composing the' 

 latter is a strongly refringent yellow substance, 

 which is found more or less abundantly in drops 

 between the ova and the yolk-cells. At first 

 these elements all lie near one another, with- 

 out distinct order or regularity. Soon, how- 

 ever, each ovum becomes surrounded by a 

 number of yolk-ceUs. They thus become balls 

 of more or less considerable size, which are 

 then pressed against the adjacent drops of 

 shell-siibstance, so that these become here and 

 there attached to the surface as flattened or 

 watch-glass shaped drops. The subsequent 

 shell arises by the thinning and consequent 

 spreading of the shell-substance over the 

 surface of the balls. While this is going on, 



Fio. 371. — Diagrammatic 

 repreaentation of the course 

 and connections o( the vagina, 

 as seen in longitudinal sec- 

 tion, v.d., vas deferens ; 

 c.p; cirrhus - pouch; v., 

 vagina ; ut., uterus ; ut.o., 

 f.c, fertil- 



uterine openmg; 



the egg has, by further inception of yolk-ceUs, ising canal ; o.d., oviduct . 



attained its final size, and the original, often »•?•' ^heU-giand. 



very irregular, form beg|m^|e&'fo°^M/cS® *^' ^'^ '' afterwards 



