486 University of California Publications in Zoology [Vol. 18 



Tsuchiya, 1913; Conor, 1914). Looss explained these failures by 

 stating that since man was the only known host for this parasite 

 experiments on other animals were without significance. Looss 's 

 hypothesis of direct infection received the support of many parasit- 

 ologists and undoubtedly delayed the final discovery of the life cycle 

 of these forms. 



The first successful experiments on the method of transmission of 

 the human schistosomes were carried on in 1909 by Japanese workers 

 with the Japanese species, Schistosoma japonicum. Katsurada and 

 Hashegawa (1910) showed that cats and dogs could be infected 

 through the skin with S. japonicum, by immersion in canal water in a 

 district where schistosomiasis was prevalent. Fujinami and Nakamura 

 (1909) succeeded in infecting calves through the skin with this same 

 parasite. The first article by these authors was in Japanese, but their 

 results were included in a later publication by Fujinami (1914) in 

 German. In their first experiments the Japanese workers accepted 

 Looss 's hypothesis that the infective stage which penetrated the .skin 

 of the host was the miracidium. Further studies, however, began to 

 throw doubt on this conclusion. Miyagawa (1912, 1913) studied the 

 infective stage just after penetration through the skin. In his de- 

 scription he noted the presence of suckers and other differences between 

 this stage and the miracidium. He therefore concluded that S. japon- 

 icum must have an intermediate host. Matsuura and Yamamoto (1912 

 and 1912«) studied infective stages of S. japonicum before they 

 entered the skin and Fujimami (1914, p. 22), with the aid of Naka- 

 mura and Narabayashi, studied newly penetrated schistosome larvae 

 in sections of new-born mice and rats. All of these workers noted 

 differences between the infective stage and the miracidium. Fujinami 

 (1914, p. 23) concluded from his studies that the miracidium did not 

 penetrate the skin in infection with S. japonicum. Tsuchiya (1913) 

 also came to the conclusion that the Japanese schistosome must require 

 an intermediate host for its development, since all attempts to produce 

 direct infection with the miracidium were without success. Katsurada 

 (1913, p. 371) in a summary of research on Japanese schistosomiasis, 

 abandoned Looss 's hypothesis of penetration by the miracidium, in 

 favor of a relatively simple metamorphosis of the miracidium prior 

 to skin infection. In this same paper published in December, 1913, 

 Katsurada (1913, p. 378) added a note to the effect that he had just 

 been informed that Miyairi of Kinshu had found the intermediate 

 stage of 8. japonicum in a species of Lymnaea} Fujinami (1914, 



1 This early identification was later corrected. 



