8 Art. 8.— S. Goto and T. Mateudaira : 



in the region of the acetabulum. From the recurrent vessel are 

 given off a number of branches which are distributed to the 

 different parts of the body. The finer ramifications of the ex- 

 cretory vessels have not been traced to our satisfaction, owing to 

 the opaqueness of the worm in the living state, and we have not 

 been able thus far to observe very young ones alive. The wall of 

 the excretory vesicle is formed by a thin epithelium of finely 

 granular appearance containing nuclei at wide intervals and resting 

 on a basement membrane. Outside this lies a single layer of fine 

 circular muscle fibres, which is continued at the apex of the ex- 

 cretory papilla into the circular muscle layer of the body wall. 

 Short inconspicuous muscle fibres running in a longitudinal direc- 

 tion may sometimes be found around the excretory pore. 



On the nervous system we have made only a few observations. 

 The brain is situated directly behind the oral sucker, on the dorsal 

 side of the prepharynx (fig. 2). It is transversely elongated and 

 presents thickenings at the two ends, where nerve cells are 

 especially numerous and from which large nerves are given out for- 

 wards, one on each side, on the dorsal side of the oral sucker and 

 another large pair backwards. The latter are the main nerves that 

 supply the greater part of thebody and can be followed for a consider- 

 able distance, lying directly on the inside of the muscular layers 

 of the body wall. A few additional nerves are shown in the figure. 



The common genital pore lies in the median line of the 

 body slightly backwards than the middle of the whole length and 

 is relatively large. It leads into a spacious genital atrium lined 

 by the direct continuation of the cuticle of the body surface and 

 indistinctly divided into a dorsal and a ventral portion, into 

 the former of which the male duct opens and into the latter 

 the metraterm. Around the genital atrium are found groups of 

 unicellular dermal glands opening by tolerably long ducts on the 

 external cuticle. 



The testes, of which there are two forming an oblique pair, 

 lie just in front of the acetabulum, with which the posterior or 

 right one may be partly overlapping (fig. 1). They are subglobular 

 and measure 175-250^ in diameter. From the front end of the 

 right testis a slender vas efferens proceeds forwards obliquely to- 



