Bilharziasis 
haei alobium contained germinal cells within its body cavity, it must, natu¬ 
rally, 'e argued, have been destined to produce sporocysts at some stage of its 
life cycle In view of this, Looss evolved the hypothesis that man acted simul¬ 
taneously caS the intermediary, as well as the definitive host of this parasite. 
According to his hypothesis the miracidia after reaching water perforated 
directly the skio of man, thence making their way to the liver. Here they 
developed into male and female sporocysts which in turn gave rise to male 
and female cercariae, and these, in their turn, developed into adult worms. 
Manson on the basis of biological analogy always opposed this view. 
Looss also denied the existence of two species of bilharzial parasites, 
basing his contention on the absence of constant morphological differences 
in the two hypothetical species. He regarded the lateral spined ovum as 
characteristic of the unfertilized, and the terminal spined ovum as the 
one associated with the fertilized female; further he maintained that he had 
seen both varieties of ova simultaneously in the uterus of the same female 
worm. 
Sambon (1907) supporting the views of Manson (1903), and Sonsino, 
wrote an able paper establishing the identity of a new species of bilharzia 
which he named Schistosomum mansoni . He based his reasoning on the diffe¬ 
rent geographical distribution of the two forms of infestation, on the different 
systems pathologically involved, and on the morphological differences in the 
ova of the two species. Looss bitterly opposed his reasoning. 
Bour (1913) failed to convey the disease to monkeys by injecting miracidia 
intravenously. 
Miyagawa (1912) described the entrance of the infesting form of S. japo- 
nicum, an allied species, through the skin of the host, to the portal system. 
Miyairi and Suzuki (1913) demonstrated that the fresh-water mollusc, since 
named Blandfordia nosophora, acted as the intermediate host of Schistosomum 
japonicum. These investigators also conveyed the disease to mice by placing 
them in water containing infested snails. Ogata (1914) accurately described 
the morphology of the cercaria of S. japonicum, and later, Leiper and Atkinson 
(1915) confirmed all these observations, in Japan. In 1915, Leiper came 
in charge of the Bilharzia Mission to Egypt. As a result of the work of this 
mission, the existence was established of two species of Schistosoma morpho¬ 
logically distinct and producing different ova. From these ova, miracidia 
are hatched, which developing in certain fresh-water molluscs, produce cer¬ 
cariae, which have slight morphological distinctions. 
The transmission of the disease to laboratory animals was effected and 
the affinity of S. haematobium for the vesical, and S. mansoni for the alimentary 
systems demonstrated. 
In 1915-16, Cawston, in South Africa, showed that a fresh-water mollusc 
Physopsis africana (a near relative of Bullinus) acts as the intermediary 
host of S. haematobium in that country, and, together with Becker, claims to 
have produced artificial infestation of this species of snail with miracidia 
