FASCIOLID^E 19 



or uncleared specimens, occupy the anterior half. In the 

 others the testicles occupy the posterior half, and the 

 uterine coils are therefore only to be seen in the anterior 

 half, in these the ovary is anterior. Two genera, Opis- 

 thorchis and Clonorchis are represented in man, but are 

 not readily distinguished from each other in uncleared 

 and unstained specimens. 



(2) Two species are known in man with the ventral 

 sucker in the middle line, and these belong to different 

 genera. 



Heterophyes heterophyes is the smallest of the human 

 flukes, and the ventral sucker is much larger than the oral. 

 Paragon imus, represented by Paragonimus westermani, is 

 a much larger and more fleshy fluke. The ventral sucker 

 is about the same size as the oral sucker. 



This grouping on external characters only is not satis- 

 factory when the parasites of other animals have also to 

 be considered, and therefore it is much sounder to group 

 according to structural differences, which in specimens 

 rendered transparent by glycerine or creasote, with or 

 without staining, can be readily made out. 



FASCIOLA. 



Fasciola. Ovary and testicles much branched. The 

 testes are posterior. Numerous branching diverticula of 

 the intestine. 



In Fasciola hepatica, which has rarely been found in 

 man, but is common in sheep and cattle, the branched 

 intestinal diverticula are all on the lateral margins of the 

 worm ; simple diverticula only on the internal aspect. It 

 inhabits the bile-ducts and gives rise to dilatation of these 

 ducts, with considerable thickening. It may cause exten- 

 sive destruction of the liver and the formation of abscesses. 

 It is a pathological curiosity in man (fig. 6). 



FASCIOLOPSIS. 



Fasciolopsis. Ovary and testes branched. Testes pos- 

 terior. Cirrhus pouch very large. Intestine not branched 



