1919] Cort: The Ccrcaria of the Japanese Blood FluJic 495 



in a fully developed cercaria or seen recorded in the literature. The 

 whole system in the body is limited to the superficial layer of paren- 

 chymatous tissue, and almost all of the anterior half of the body of 

 the cercaria is without flame cells. However, the total mass of the 

 body of the cercaria is so small that no part is far from a flame cell. 

 I will not discuss here the general homologies of the excretory system of 

 the forked-tailed cercariae, since this subject was taken up in previous 

 publications (Cort, 1917, 1918). Previous knowledge of the excretory 

 system of the cercaria of the human schistosomes is very slight. 

 Miyagawa (1916, p. 67, pi. 4, fig. 30) saw only the main tubules of 

 the excretory sj^stem in the body and missed its connections in the tail. 

 Miyairi and Suzuki (1914) stated that the excretory sj^stem of the 

 cercaria of S. japonicum has five pairs of flame cells. Ogata (1914) 

 found two paired, laterally symmetrical flame cells with vessels. Iturbe 

 (1917, p. 433, fig. 1) located five pairs of flame cells in the cercaria of 

 8. mansoni, including one pair in the tail, but neither describes nor 

 figures the rest of the system. From my knowledge of the homologies 

 of the excretory systems of the fork-tailed cercaria in general I would 

 expect to find this system in the cercariae of 8. mansoni and 8. 

 haematohium corresponding closely to the conditions just described 

 for the cercaria of 8. japonicum. 



The central nervous system of the cercaria of 8. japonicum (figs. 

 1, 2, n) is a bilobed mass back of the oral sucker and dorsad to the 

 ducts of the cephalic glands. No attempt was made to trace the nerve 

 trunks leading from this mass. 



It was not possible to distinguish morphologically between male 

 and female cercariae, and the only trace of the complicated reproduc- 

 tive systems of the adult is a small mass of nuclei on the ventral side 

 back of the acetabulum (fig. 1, /■)• The extreme immaturity of this 

 type of cercaria is emphasized when we consider how completely the 

 structure of the adult schistosomes is dominated by secondary sexual 

 characters and the complex reproductive systems. 



The digestive system of the cercaria o-f 8. japonicum is in a very 

 rudimentary condition (figs. 1, 2, m, ds). The mouth is situated on 

 the ventral surface a little distance back of the anterior tip. A very 

 narrow buccal cavity passes through the oral sucker. The esophagus 

 extends from the posterior limit of this cavity to about the midline 

 of the body dorsad to the cephalic glands, where it widens into a 

 heart-shaped structure which represents the beginnings of the bifur- 

 cations of the intestinal caeca. The remarkable thing about this 



