16 Art. 4.— S. Goto and H. Kikuchi : 



the cell boundaries of which are fairly distinct in sections, and the 

 nuclei of which are relatively large, round and vesicular in 

 appearance. This species has the power of sucking out the blood 

 of the host and the contents of the intestine consist of blood 

 corpuscles and mucous cells of the host in all stages of digestion. 



The general arrangement of the excretory vessels is similar to 

 that of Dactylogyrus. The openings lie on either side of the body 

 close to the lateral margin, at the level of the hind end of the 

 pharynx. Each one leads backwards into a terminal vessel, 

 which enlarges into a club-shaped vesicle lying on the ventral side 

 of the intestinal ccecum. From the hind end of this terminal 

 vesicle starts tbe principal posterior vessel, which proceeds back- 

 wards on the ventral side of the intestinal cœcum, at whose hind 

 end it suddenly bends towards the median line and is connected 

 with the corresponding vessel of the other side by a short commis- 

 sure; it then turns back and retraces its former course and 

 becomes very fine at about the level of the genital opening. 

 Close to and just in front of the origin of the posterior vessel, the 

 terminal excretory vesicle gives rise to a vessel which immediately 

 divides into two and are distributed to the anterior parts of the 

 body, where one of them is directly continued into the corres- 

 ponding vessel of the other side in the region of the brain. 

 From the main vessels above mentioned are given off numerous 

 branches which terminate in the Avay generally known for 

 flatworms. 



Among more recent writers Maclaren [p. 500] divides the 

 Gyrodactylldœ into two groups, in the first of which the vagina is 

 present and the excretory canals open behind, while in the second 

 the vagina is absent and the excretory canals open in front, and 

 he assigns Tetraonchus, Dactylogyrus, Amrphibdclla and Diplectanum 

 to the first, and Gyrodactylus and Calceostoma to the second. But 

 in view of our observations on Dactylogyrus and Tetrancistrum, a 

 near ally of Ancyrocephalus ( = Tetraonchus), the above division, so 

 far as it refers to the opening of the excretory system, is no longer 

 tenable. 



