40 THE LIVER-FLUKE. 



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 fully withdrawn a slight cavity, the 'genital 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. 



II. LIFE-HISTORY OF THE LIVER-FLUKE. 



The free- swimming larvae, may be obtained by removing 

 e 99 s from the bile-ducts of an infected sheep and hatching 

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

 and redioe may be obtained from specimens of Limn sea trun- 

 catula, kept in the same vessel. 



The main features in the life-history are as follows. 



A. The First Generation is produced sexually by the develop- 

 ment of fertilised ova. 



1. The eggs, laid in large numbers in the bile-ducts of the 

 sheep or other infected mammal, pass with the bile 

 into the intestine, and so escape from the body. 

 They are ovoid bodies "005 inch long and '003 

 inch broad, enclosed in smooth brownish chitinous 



