138 Beport of the Bilharzia Mission in Egypt, 1915 



the oral sucker in the adult as occurs in the amphistomes. Without 

 definite evidence it was, therefore, impossible to coma to a trustworthy 

 conclusion regarding the absence of a pharynx in the cercaria of bil- 

 harzia. 



Happily such evidence was now procurable as a result of the discovery 

 of the "invasion forms" of B. japonica by Fujinami and Miyagawa. 

 From the description of these bodies, which were said to possess oral and 

 ventral suckers and a developed gut, it was evident that they were infecting 

 cercarias, but there was no mention, in either paper, of the presence or 

 absence of a pharynx. 



It was obviously necessary to establish this point by actual observation, 

 not merely by inference, if it was to be utilized as a basis for experimental 

 work. 



My plan then was, in 1912, to proceed to Japan, and by repeating the 

 original experiments or by examining the original preparations to settle 

 this question ; to confirm the expected value of the clue by examining the 

 molluscs of the district where Fujinami has conducted his immersions and 

 which was known to be intensely infected ; and thence to proceed to 

 Africa. If one or more of the molluscs there was found to contain 

 cercariaB exhibiting this peculiarity, then it would be possible to attempt 

 the experimental transmission of bilharzia to monkeys with every prospect 

 of success. 



These plans were, however, subject to other counsels and it was not 

 until the summer of 1914 that I felt free to carry out my original scheme. 

 This I was then enabled to do fully, thanks to the cordial co-operation of 

 Professor Fujinami. Through him I was able to examine the " invasion 

 forms " and to establish the value of my morphological clue by a visit to 

 the rice fields of Katayama, where the ease with which the test could be 

 applied to the molluscs in an endemic area was quickly demonstrated. 

 With cercarise exhibiting this morphological peculiarity, mice were 

 afterwards infected successfully with B. japonica. 



In the meantime, however, Miyairi and Sudzuki, as related above, had 

 succeeded by another method of approach in tracing the metamorphosis in 

 a closely allied, if not identical, snail, in the South Island of Japan. My 

 own observations therefore confirmed generally the results of these 

 workers, apart from establishing my chief, ulterior object ; which was to 

 provide a simple and reliable means of attacking the complex problems 

 of B. hcematohia. 



In regard to details, concerning which only the abstract by Kumagawa 

 was available, I was unable to confirm the presence of " rediae " in the 

 development of B. japonica. From my own observations I had concluded 

 that the B. cercarice originate in sporocysts. I was not in a position, 

 pending fuller information, to decide whether these " redise " were actually 

 developmental stages of bilharzia or of some other species with which the 



