NOTES ON DISTOMA ENDEMICÜM. 51 



used for manuring purposes. I frequently observed farmers transport- 

 ing manure in boats on the ditch and unrestrainedly cleaning their 

 manure-tubs in the water. Here are undoubtedly chances enough for 

 millions of Distoma-eggs to reach the ditch-water, in which ciliated 

 embryos would hatch out. Indeed it admits of hardly any doubt that 

 the ditch-water stands in intimate relation with the development of our 

 parasite; and one can not be going too far in asserting that the 

 establishment of a new system of water-supply would ensure the 

 annihilation of Distoma-disease, so far as the above mentioned villages 

 are concerned. 



The question into what animal those ciliated embryos next find 

 their way must remain unanswered for the present. After the analogy 

 of those Distomes whose life-history has been worked out, I naturally 

 fixed my attention on molluscs. I found in abundance Limnaea japonica 

 Jay, Melania libertina Gould, and a small species of Paludina. Less 

 abundant were a large species of Paludina, and species of Planorbis, 

 Cyclas, Corbicula and Anodonta. Land-snails were said to be exceed- 

 ingly rare. Notwithstanding the special search made, I failed to discern 

 any trace of Sporocyst, Kedia or Cercaria in any one of these molluscs. 

 Dr. Kiyono informed me that some years ago he found Sporocysts 

 or Rediaî, whichever they were, in almost all Melania of the same 

 locality that he examined. Unfortunately I was unable to verify this 

 fact myself. It is less probable, although the possibility should not be 

 excluded, that the ciliated embryo should first enter into some other 

 invertebrates. At any rate it requires no comment to assume that 

 somehow broods of Cercaria would finally be formed. As to the way 

 in which these Cercarias become introduced into the human body, one 

 might think of four alternatives. Firstly, they may enter it together 

 with water that is drunk. Baelz does not hesitate to assume this as the 

 way of infection ; but I am inclined to put some doubt on this point, 



