REPRODUCTIVE SYSTEM 31 



from the vesicula seminalis to the end of the 

 penis. When the penis is withdrawn this duct 

 is thrown into convolutions. 



e. The penis is a large muscular organ which lies, 



when withdrawn, within the cirrus-sac, a space 

 in front of the ventral sucker. It can be pro- 

 truded by evagination, and the ejaculatory duct 

 then lies within it. 



f . The cirrus-sac is situated between the ventral sucker 



and the genital aperture. The penis lies in it 

 when withdrawn, as do also the vesicula semiaalis 

 and a small accessory gland which surrounds the 

 ejaculatory duct. 



The female organs. 



a. The ovary is branched and tubular : it lies on the 



right side in front of the anterior testis, and its 

 branches unite to form the narrow ovarian duct. 



b. The yolk-glands are very numerous small rounded 



masses, scattered along two areas extending 

 along the sides of the body from end to end, and 

 each nearly one quarter of the width of the whole 

 worm. 



0. The vitellarian ducts, or ducts of the yolk-glands, 

 unite to form an anterior and a posterior duct on 

 each side. These unite about the junction of the 

 anterior and middle thirds of the animal, forming 

 a transverse duct, which runs inwards to open 

 into the median yolk-reservoir: from this a 

 single median vitellarian duct runs a short dis- 

 tance forwards and unites with the ovarian duct 

 to form the oviduct. 



Close to the junction is the opening of a short 

 duct, the ' vagina ' or ' canal of Laurer,' which is 

 said to open to the exterior on the dorsal surface. 



d. The shell-gland is a median glandular mass sur- 

 rounding the junction of the ovarian and median 

 vitellarian ducts. 



