242 



ZOOLOGY 



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, 

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



ov- 



FiG. 188. — Fasciola hepatica. Internal organisation. General view uf the anterior portion 

 of the body, showing the various systems of organs as seen from the ventral aspect, eo- 

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

 rest is not shown) ; od. commencement of oviduct ; ov. ovary (germarium) ; p. cirrus ; jsA. 

 pharynx ; sh. sheU-gland : te. testes ; v.t. uterus ; vd\ left vas deferens ; vd^. right vas 

 deferens ; vit lobes of vitelline glands ; v&. vesicula seminalis. (After Sommer.) 



posterior end and giving off numerous branches. There are no 

 organs of special sense. 



The reproductive organs (Fig. 188) 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 

 testes, vasa dcferentia, and cirrus. The testes (te.) are two greatly 



