V PHYLUM PLATYHELMINTHES 249 



The reproductive organs (Fig. 194), repeated in each fully 

 formed proglottis, are in essential respects very similar to those of 

 the Liver-Fluke. In the most anterior proglottides they are not 

 developed ; it is only at about the 200th proglottis that they first 

 appear : at first the male parts of the system are alone differen- 

 tiated ; then in the succeeding proglottides, till we approach near 

 the posterior extremity of the body, the female organs are like- 

 wise developed. In the most posterior segments modifications 

 and reductions of some of the parts take place, owing to the great 

 increase in size of the uterus. The male portion of the apparatus 

 consists of the testes with their efferent ducts, the vas deferens 

 (vas. def.), and the cirrits, with its sac. The testes consists of 

 numerous rounded lobes situated nearer the dorsal than the 

 ventral surface, and extending throughout the greater part of the 

 length and breadth of the proglottis. With each lobe is con- 

 nected a fine efferent duct ; the ducts of neighbouring lobes unite 

 together to form somewhat larger ducts ; and the larger ducts, 

 receiving numerous tributaries, eventually open into the inner 

 extremity of the vas deferens, or main duct of the testis. The 

 vas deferens is a convoluted tube which extends outwards towards 

 the lateral margin (right or left as the case may be) of the 

 proglottis. 



The terminal part of the vas deferens, which is somewhat nar- 

 rower than the rest, traverses a narrow protrusible process, the 

 cirrus, and opens at its extremity by the male genital aperture in 

 the genital atrium or cloaca. The cirrus is enclosed at the base 

 by a muscular sac, the cirrus-sac. 



The ovary {germarium) (ov.) differs from that of the Liver- 

 Fluke in being a paired organ, consisting of two approximately 

 equal, right and left, halves. It is situated towards the posterior 

 border of the proglottis. Like that of the Liver-Fluke, it consists 

 of a number of branching tubes, in the interior of which the ova 

 are developed. From opposite sides these tubes converge towards 

 the median line, where they open into the oviduct. A yolk-gland 

 {gl. vit.), of less relative extent than in the Liver-Fluke, consists 

 of a number of minute lobules ; a duct, the yolk-duct, which runs 

 forward from it, opens into the oviduct. The numerous lobules of 

 a rounded shell-gland (schld.) surround the yolk-duct where it passes 

 forward to join the oviduct ; and the many shell-gland ducts open 

 into the oviduct near its junction with the yolk-duct: this part of 

 the oviduct is the ootype — the part in which the egg becomes 

 completed. In front this passes into the uterus. The female 

 genital pore, situated in the genital atrium, leads into a narrow 

 passage which runs inwards and backwards towards the middle 

 line of the proglottis, where it ends in a dilatation usually filled 

 with sperms — the receptaculum seminis. From this a narrow duct 

 — the fertilising duct or spermatic duct — runs to join the oviduct. 



