ZOOLOGY SECT. 



The Liver-Fluke- has a well differentiated nervous system, 

 which shares in the prevailing bilateral arrangement of the parts. 

 The central part of this system consists of a ring of nerve matter 

 which surrounds the oesophagus, and presents two lateral thicken- 

 ings, or ganglia, containing nerve-cells, and a single ganglion in the 

 middle line below. From this are given off a number of nerves, 



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FIG. 177. Distomum hepaticum. Internal organisation. General view of the anterior 

 ] tort ion of the body, .showing the various systems of organs as seen from the ventral aspect. 

 './'. ejaculatory duct ; /. female reproductive aperture ; int. anterior portion of the intestine- 

 (the rest is not shown) ; od. commencement of oviduct ; or. ovary ; /i. penis ; ,>l. pharynx ; 

 xli. shell gland; to. testes ; vt. uterus ; r^ 1 . left vas cleferens ; <(/-. right vas deferene 

 lobes of vitelline glands ; vs. vesicula seminalis. (After Somuier.) 



of which the chief are a pair of lateral cords running back to the 

 posterior end and giving off numerous branches. There are no 

 organs of special sense. 



The reproductive organs (Fig. 177) are constructed on the 

 hermaphrodite plan, i.e. both male and female organs occur in 

 the same individual. The male part of the apparatus consists of 



