TBEMATODA 25 



tive feature of the parasite's organisation (k). In consequence 

 of injury to the specimen which is here drawn, the upper testis 

 (i) displays no seminal tubes. I made out the female reproduc- 

 tive organs with more completeness. In the outline drawing 

 given in my introductory treatise I had indicated the probable 

 position of the uterine folds ; reducing the organ to the simplest 

 expression of what I concluded must obtain in the normal 

 condition. My conjecture was perfectly correct. The uterus 

 consists of irregularly folded tubes, which, though here and 

 there apparently branching from a central tube, are in reality 

 folded evenly upon themselves. The oviduct can be distinctly 

 traced to its outlet in the reproductive papilla, which, as usual 

 in true Distomes, is placed in the middle line, immediately 

 above the ventral sucker. In my examination of Mr Busk's 

 original specimens I could not find the slightest trace of 

 vitelligene organs; but in my fresh examples I not only 

 obtained proof that these organs were largely developed, 

 but that their limitations could be fixed with accuracy (g g}. 

 They consisted of two large elongated masses, one on either 

 side of the body, occupying about two thirds of the entire 

 length of the parasite. Their yolk-vesicles were distinctly 

 seen ; but the main efferent canals were only here and there 

 traceable. Clearly, the position and character of the yolk- 

 forming glands of this large human fluke are quite unlike those 

 of any of its congeners. This fluke is a remarkably fine 

 species, and, when viewed in the fresh state with a powerful 

 pocket-lens, presents a most striking appearance. I did not 

 observe any cutaneous spines. I found the eggs to present an 

 average long diameter of about ~", by ^ in breadth. They 

 are therefore somewhat smaller than those of the common fluke. 

 In the specimen preserved in the Hunterian Museum there was 

 complete evidence of the presence of an excretory outlet at the 

 caudal extremity ; but I did not succeed in finding any trace of 

 the water-vascular system higher up. I have no doubt, how- 

 ever, that it exists. 



As regards the affinities of Distoma crassum, it is clear that 

 this Trematode has little in common either with the liver-fluke 

 of cattle and sheep (Fasciola hepatica), or the still larger species 

 obtained by me from the giraffe (Fasciola gigantea). The 

 simple character of the digestive tubes obviously connects it 

 more closely with the lancet-shaped fluke (Distoma lanceolatum), 

 the last-named parasite being, as already shown, an occasional 



