Previous Work on B. japonica 139 



snails, experimentally infected with miracidia, had been naturally infected 

 previously.' 



On my return voyage, after the outbreak of war, I visited Egypt and 

 found that though the results of the recent work on B. japonica \\ eve known 

 there, it was still held that they gave no solution to the special problems 

 presented by the B. liccmatohia. 



Considering that the new facts derived from my own observations on 

 B. japonica would enable me to overcome the experimental difficulties 

 which had hitherto surrounded the Egyptian question and realizing the 

 immediate importance of some simple and efficient prophylactic measures 

 for the large bodies of troops then proceeding to Egypt, I sought and obtained 

 the occasion for the investigations in Egypt related in this report. A study 

 of the accounts given by Sonsino and Looss of the cercarite found by them 

 in the course of their search showed that they had not seen and passed 

 over the B. cercarice. The bulk of their cercarise possessed a distinct 

 pharynx. In a few it was absent but in these there was merely an oral 

 sucker without any development of oesophagus or gut. It was evident that 

 these forms had still to undergo maturation before they could become 

 infective to their definitive hosts and as some possessed a definite 

 perforating spine and other peculiarities of forms that undergo encystment 

 in fishes and other secondary hosts, these cercariae were readily excluded. 

 It was therefore necessary to find further cercarise which had hitherto been 

 overlooked. The search for this was made by the method of intensive study 

 of a small heavily infected area. The fact that B. japonica developed in a 

 genus of the family hydrobiidas was of no assistance. Indeed by those 

 unversed in the bionomics of helminths this might have been taken, 

 disastrously, as an additional and invaluable analogy. In point of fact the 

 Egyptian bilharzia worms were found to infest two genera of freshwater 

 moUusca belonging not merely to a different family but to a different order. 

 In other words, B. japonica and B. hcumatohia (s. lat.) were found in snails 

 as distantly related in classification as are the lice to the mosquitoes. In 



' In Egypt we found commonly present in the species which were actually intermediaries 

 for the various Bilharzia cercavicB additional developmental forms ; some developing in rediaj 

 and other, bifid-tailed, forms developing in sporocysts which bore a superficial resemblance 

 to B. cercarice. It is obvious from the illustrations given by Cawston that such forms 

 were mistaken by him for B. cercarice. Thus, prior infections may prove a serious 

 source of fallacy to those endeavouring to advance experimentally from the miracidia 

 unless the results are carefully checked by the morphological method. 



In a report written on my return from China in October, 1914, I had to content myself 

 with the statement that my results confirmed Miyairi's main conclusion, and that in the 

 absence of any accessible publications a comparison of the detailed conclusions was for 

 the present impossible. Apparently during the closing months of 1914, Miyairi and 

 Sudzuki pubUshed in Japan, in German text, a detailed account of their findings. 

 From this, which is well illustrated, it is now evident that divergence of view regarding 

 these "rediic" is due solely to a difference in interpreting the same structures. 



