LIFE HISTORY. 33 



Close to the junction is the opening of a short 

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

 opens externally in the middle line on the dorsal 

 surface. 



d. The shell-gland is a median glandular mass, really 



an aggregate of unicellular glands, surrounding 

 the junction of the ovarian and median vitellarian 

 ducts. 



e. The oviduct, or ' uterus,' is a wide, much-convoluted 



tube, commencing at the point of union of the 

 ovarian and vitellarian ducts in the midst of the 

 shell-gland, and lying between the shell-gland 

 and the genital aperture. Its convolutions extend 

 halfway across the animal, and numerous eggs 

 can be seen within it. 



f. The aperture of the oviduct is at the base of the 



penis, and on its left side. When the penis is 

 fully withdrawn a slight cavity, the 'genital 

 sinus,' is formed, into the left side of which the 

 oviduct then opens. 



B. The Nervous System. 



This cannot be made out with certainty in specimens 

 prepared as above. It can be seen in a specimen rendered 

 transparent by caustic potash, though such preparations are 

 very perishable. It may also be made out in sections. 



It consists of a nerve-collar round the pharynx, with two 

 lateral ganglia and a median ventral one. From these arise 

 nerves, of which two large lateral ones are the chief. These 

 two run backwards, one on each side of the body (fig. 13). 



II. LIFE HISTORY OF THE LIVER-FLUKE. 



The free-swimming larv® may be obtained by removing 

 eggs from the bile-ducts of an infected sheep and hatching them 

 in a shallow vessel of water in a warm room. Sporocysts and 



