PHYLUM PLATYHELMINTHES 



251 



(Rhabdoccele Turbellaria (Fig. 200), a few Trematoda), with or 

 ithout short lateral diverticula. In the maj ority of the Trematodes 

 consists of a pair of simple canals ; but in some, as in the Liver- 



IG. 200. General plan of the 

 structure of a Rhabdoccele 

 Turbellarian. b. c. bursa 

 copulatrix ; en. brain ; e. eye ; 

 g. gennarium ; i. intestine ; 

 In. longitudinal nerve ; m. 

 mouth; ph. pharynx; rs. 

 receptaculuin seminis ; g. uni- 

 cellular glands; t . testis ; u. 

 uterus ;. vs. vesicula semin- 

 alie ; <J ejaculatory duct ; 

 <J $ common genital aper- 

 ture. (After Von Graff.) 



OV 



>1. General plan of the structure of a Poly clad. en. brain ; 



:ye ; i. intestine ; In. longitudinal nerve cord ; m. mouth ; 



FIG. 201. General 



ovary; ph. pharynx; phi. sheath of pharynx; t. testes ; u. 

 uterus ; i-d. vas deferens ; vs. vesicula seminalis ; <$ male 

 aperture ; $ female aperture. (After Von Graff.) 



fluke, there is a pair of canals which give off numerous branches. 

 In the Polycladida (Fig. 201) there is a central cavity from which 

 numerous branching canals are given off. In the Tricladida (Fig. 

 202) one median canal passes forwards from the pharynx, 



