228 



ZOOLOGY 



!SE(.T. 



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, 



vii 



pb., 



'p 



n 

 



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



(th 



nil. shell 

 lobes of 



gland; to. testes ; v.t. uterus; nfl-. left vas deferens ; . right vas deferens : 

 vitelline glands ; vs. vesicula seminalte. - (After Sommer.) 



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 



