240 



ZOOLOGY 



SECT. 



branched tube situated on the right-hand side in front of the 

 testes ; the branches open into a common narrow tube, [the 

 oviduct (od.). The vitelline glands (vit.) consist of very numerous, 

 minute, rounded follicles, which occupy a considerable zone in 



the lateral regions of the body. On 

 each side are two large ducts, 

 anterior and posterior, uniting to 

 form a single main lateral duct, 

 right or left ; and these run nearly 

 transversely inwards to open into a 

 small sac, the yolk reservoir. From 

 this a single median vitelline duct 

 runs forwards for a short distance to 

 join the oviduct. Around the junc- 

 tion are grouped a mass of unicellular 

 shell-glands or accessory female glands 

 (sh. gl.), each of which is produced 

 into a narrow process or duct opening 

 into the end of the oviduct in the 

 region of the latter to which the term 

 ootype is applied. The uterus (ut.) 

 is a wide convoluted tube, formed 

 by the union of the oviduct and 

 median vitelline duct ; in front it 

 opens close to the base of the cirrus. 

 When the cirrus is withdrawn, a small cavity, the genital atrium or 

 cloaca, is formed common to the external apertures of both male 

 and female ducts. A canal, termed the canal of Laurer, leads 

 from the junction of the oviduct and median vitelline duct to 

 open externally on the dorsal surface. 



Development. Each ovum on impregnation is surrounded 

 by a mass of vitelline matter or yolk derived from the v oik- 

 glands. It then becomes enclosed, while passing through the 

 ootype, in a chitinous shell, the substance of which is usually said 

 to be derived from the shell-glands. 1 The completed egg remains 

 for a little time in the uterus ; eventually it is discharged, and, 

 passing down the bile-ducts of the Sheep into the intestine, 

 reaches the exterior with the faeces. Active development only 

 begins at this stage, and, three to six weeks later, a portion of 

 the egg-shell at one end becomes separated off as a sort of 

 lid or operculum, and gives exit to the contained embryo. This, 

 the ciliated embryo or miracidium (Fig. 193, A), is a somewhat 

 conical body covered all over with vibratile cilia, and with two 

 spots of pigment, the eye-spots (eye), near the broader or anterior 



1 The agency of the shell-glands in producing the material of tho egg-shell 

 is not universally acknowledged. This point will be referred to in the section 

 dealing with the general organisation. 



v.d 



Fio. 192. Fasciola hepatica. Ter- 

 minal partfof the reproductive appa- 

 ratus, ej. ejaculatory duct ; /. female 

 aperture ; g. unicellular glands ; od. 

 terminal part of oviduct (uterus) ; 

 p. cirrus ; ps. cirrus-sheath ; s. 

 sucker ; v. d. vasa deferentia ; . s. 

 vesicula seminalis. (After Sommer.) 



