590 TREMATODA 



The miracidia quickly hatch when placed in water in the tropics, 

 and swarm around Planorbis boissyi, into v/hich they disappear 

 so rapidly that in twenty minutes none will be visible in the water. 



Fig. 232. — Planorbis boissyi Potiez and Michaud, 1838. 



They pass to the liver of the mollusc and form sporocysts, rediae, 

 and cercariae, and finally end in cercariae, which, leaving the snail 

 and swimming about the water, enter the skin or mucosa of the 

 mouth or throat; and so infect 



man. 



Pathogenicity. — 5. mansoni is 

 the cause of intestinal schisto- 

 somiasis (Chapter LXXIX.). 



Fig. 233. — Sporocysts of Schisto- 

 soma mansoni Sambon, 1907, still 

 Partially Embedded in Tissue 

 FROM THE Liver of the Planorbis . 



(After Leiper, from ' Researches 

 on Egyptian Bilharziosis,') 



Fig. 234. — Cercaria of Schistosoma 

 mansoni Sambon, 1907. 



(After Leiper.) 



Schistosoma japonicum Katsurada, 1904. 



Synonym,— -Schistosomum cattoi Blanchard, 1905. 



Definition. — Schistosoma with a nearly smooth cuticle. Male 

 with a few spines or protuberances along the margins of the gynse- 

 cophoric canal in the fresh condition. Testes six to eight, irregularly 

 elliptical. Intestinal caeca unite very late and form a very short 

 intestine. Female with ovary almost in the middle of the body. 

 Vitellaria do not reach the posterior extremity. Uterus long, with 

 many eggs, showing small lateral spines or thickenings. Develop- 

 ment of cercaricB in species oiBlanfordia. 



History. — ^For several years an endemic disease, characterized by 

 enlargement of the liver and spleen, fever, diarrhoea with mucus 

 and blood in the motions, associated with ascites and cachexia and 

 extreme weakness, had been observed in the provinces of Yamanashi 



