TREMATODA 



135 



apparently the same relations as the " canal of Laurer " of the 

 Digenea, except that the latter opens to the exterior direct. 

 F. V. T.]. 



The oral cavity, the oesophagus, and the pharynx with its pharyn- 

 geal bursa, are lined with a continuation of 

 the cuticle of the body ; the . intestinal 

 branches are lined with high cylindrical 

 epithelium (fig. 67). The oesophagus and 

 intestinal branches also have often one 

 layer of annular and longitudinal mus- 

 cles ; the pharynx has essentially the struc- 

 ture of a sucker (fig. 69). 



The accessory organs of the alimentary 

 canal consist of groups of unicellular SALI- 

 VARY GLANDS that discharge into the 

 oesophagus in front of or behind the 

 pharynx, or even into the pharynx itself. 



The food of the Trematodes consists 

 of cutaneous mucous, epithelial cells, the 

 intestinal contents of the hosts, and often 

 also of blood, and this not only in those 

 species living in the vascular system, or in 

 the intestine or biliary passages of their 

 hosts, but also in species living as ectopara- 

 sites. 



The final products of assimilation which 

 are soluble in the fluids of the body are 

 distributed throughout the parenchyma 

 and are thence expelled by a definite 

 tubular system (excretory apparatus, proto- 

 nephridia, formerly also termed the water- 

 vascular system). This system, which is FlG> ;o- _ AUocreadium 

 distributed throughout the entire body isoporum (Looss). 38/1. Ex- 



. . ,- 11 i i i i cretory apparatus. Of the 



(fig. 70) IS Symmetrically developed, and, other organs, the oral sucker, 

 in the mOHOgenetic (ectoparasitic) Tre- Pharynx, genital pore, ab- 



dominal sucker, ovarium and 

 testes are sketched in ; the 

 cylindrical excretory bladder 

 is in the posterior end. (After 



matodes it opens, right and left, at the 



anterior end of the dorsal surface ; in all 



other species, however, it opens singly into Looss.) 



the excretory pore (foramen caudale) at 



the centre of the posterior border ; in those cases, however, where 



a sucker is present at the posterior end, as in the Paramphis- 



tomidea, the excretory pore is situated on the dorsal surface close in 



front of the sucker. 



