8 Beport aj the Bilharzia Mission i)i Egypt, 1915 



dagli altri generi di distoiui offra ancora questa singolarita di avere 

 per ospiti interiuediarii animali di classi diverse da quelle che 

 servono alio ©viluppo degli altri distomi o qnella di compire tutto 

 il suoSi^ilo vitale in parte libero nell' acqua e in parte parf^ita in un 

 solo ospite finale e iov^e senza rtproduzione alternante." 



In 1893-94, no fewer than three special missions visited North 

 Africa to investigate Bilharzia transmission. Sonsino, then 

 lecturer on parasites in the University of Pisa, proceeded to Tunis 

 from Italy. The French Government sent Professors Lortet and 

 Vialleton to Egypt. The University of Leipzig provided funds 

 for Dr. Looss, Assistant to Professor Leuckart, to proceed to 

 Alexandria. 



Sonsino [4(39] reported that, after many experiments with dif- 

 ferent kinds of fresh-water molluscs (including Melania tubercu- 

 lata, Melanopsis praemorsa and ? Amnicola similis) and arthro- 

 pods, he li;id succeeded in obtaining evidence that a small crustacean 

 was an infected intermediary host of Bilharzia ; that the Bilharzia 

 had a life-history differing from the typical one of the digenetic 

 treniatodes, as represented by Fasciola hepatica ; that it required 

 an intermediary host and underwent a metamorphosis, without 

 asexual (or alternation of) generation, "thus resembling the 

 holostoiues " ; that the free embryo having effected an entrance 

 proceeded to encyst itself and that the encysted larva, being 

 transferred with the crustacean in drinking water to the human 

 stomach, was then set at liberty. After penetrating the intestinal 

 walls, it arrived in the portal vein, where, presumably, it completed 

 its development. 



Further work led Sonsino [471], in the following year, entirely 

 to withdraw these conclusions as untenable. In the same article 

 he records without comment the discovery of larvae in Melania 

 tuberculata which he refers to Cercaria ocellata and which, as 

 will be shown later in this report, is closely allied to Bilharzia. 



Lortet and Vialleton [303] failed to transmit the disease directly 

 to animals by feeding and inoculation, or to obtain infection of 

 plants, aquatic arthropods, or molluscs ; the following species of mol- 

 1ii>-c;l being specifically mentioned : Unio aegyptiacus, Corbicula 

 consobrina, Physa acuta, Vivipara unicolor, Lanistes carinatus, 

 Lanistes boltenianus, and Melania tuberculata. 



Further experimental work was done by Lortet at Lyons in 

 France, with several local species of Limnsea, but without success. 



Later, in 1905, Lortet [302] published these " Experiences nou- 

 velles sur le developpement et la mode de penetration du Bilharzia 



