592 



TREMA TOD A 



to the gills and the wall of the aHmentary canal, where in twelve 

 days the first rediae appeared and gradually concentrated in the bile- 

 ducts, where they grew and formed second 

 rediae. Mice were immersed in the water in 

 which the full-grown snails were kept, and 

 after three weeks many 5. japonicum speci- 

 mens were found in their livers. 



In 1914 Leiper confirmed this work in Japan, 

 having recognized morphologically the cer- 

 carise originating in sporocysts, mistermed 

 — ^^^^^ by the Japanese authorities. The 



Schistosoma japoni- mollusc in question was named Katayama 

 cum. (After Leiper.) nosophora. Katayama is a synonym of 

 Blanfordia. 



In 1916 Narabayashi showed that man, cattle, horses, goats, pigs, 

 cats, and dogs, are naturally infected by 5. japonicum, which con- 

 tains ferments which can digest albumen in an alkaline medium. 

 He also found that in dogs and guinea-pigs, after penetrating the 

 skin, most of the parasites enter the venous blood- stream, though 

 some few enter arteries or lymphatics. Eventually they all enter 

 the right side of the heart and are scattered all over the lungs, at 

 the bases of which they collect and then migrate through the 

 mediastinum, diaphragm, and liver into the portal system, while 

 a few re-enter the circulation and reach the rectum. 



Morphology. — In general it resembles S. hcematohium, but the 

 cuticle of the female is smooth and that of the male has only the 

 few spines mentioned above. There are no ' bosses.' 



Male. — 8-19 millimetres in length, 0-53 millimetre in breadth, with 

 acetabulum larger than oral sucker. (Esophagus with two bulbs. 

 Junction of intestinal caeca far back, and united intestine only one- 

 fifth to one sixth of body length. The lateral excretory canals open 

 into a dorsal pore. Testes six to eight in anterior part of hind body, 

 from which the vasa efferentia unite into a common vas deferens, 

 which opens just behind the acetabulum. Seminal vessels present. 



Female. — 8-26 millimetres in length and about 0-4 miUimetre 

 in breadth. Suckers armed with fine spines. Body thicker behind 

 ovary, behind which gut forks unite. Ovary elliptical, dilated 

 behind, where the oviduct arises, and running forwards joins the 

 vitellarian duct. Vitellaria well developed, lying behind the 

 ovary, but not quite reaching the posterior end of the body. 

 Shell gland at the junction of the oviduct with the vitellarian duct. 

 Canal forms an ootype, and then becomes the uterus, which opens 

 just behind the acetabulum. 



Life-History.' — 'The eggs vary from 50 to 300, and in utero are soft, 

 and so can form various shapes. Ex utero they are oval, faintly 

 yellow, and double-contoured, 83-5 x 62-5 microns, and have small 

 lateral spines or thickenings, and at the opposite side cap-like 

 thickenings. 



The miracidia hatch out quickly and develop into cercariae in 



