LIVER DISTOME. 



273 



Guinea pigs by forcing some flesh of infested Pseudorasbora parva 

 into their gullet. After several days their liver was found to be 

 infested by many distomes of the identical kind. 



The encysted fish distome in question is found in the whole muscular 

 parts and subcutaneous tissues of the host. The worm, when freed from 

 its cyst (fig. 2\ measures 0,5 mm. in length and 0,1 mm. in breadth ; 

 the body tapers posteriorly ; the skin (" cuticula ") is armed with very fine 

 spines, which are conspicuous in the younger stages (fig. 3) but later 

 disappear ; the whole body is dotted with yellowish pigment. The oral 

 and ventral suckers are distinct, the latter being situated in the anterior 

 part of the posterior half of the body. The muscular pharynx and 

 the bifurcation of the intestine can be recognized. Posteriorly to the 

 ventral sucker there lies the terminal vesicle of the excretory organ 

 containing highly refracting granules and opening externally at the 

 posterior end of the body. The lateral vessels arise from the antero- 

 lateral corners of the terminal vesicle and running along the lateral margin 

 of the body, reach to the height of the pharynx. The freed distome executes 

 a leech-like movement. The cyst (fig. 1) is ovoidal or elliptical in 

 shape, measuring 0,13 mm. by 0,1 mm. The distome constantly rotates 

 in the cyst, in which it lies with the body folded on itself. Three hours 

 after being fed to the cat, the parasite is free from its cyst and creeps 

 about actively, some already reaching the duodenum in this way. 

 Fifteen hours after infection the parasite is found in the gall bladder. Six 

 days after, the distome is considerably elongated and measures 1 mm. 

 in length and 0,1 mm. in breadth ; the terminal vessel of the excretory 

 organ is also elongated ; the sexual organs are not yet apparent. Twelve 

 days after, the parasite measures 3 mm. in length and 0,5 mm. 

 in breadth, and the sexual organs (testes, ovary and uterus, etc.) can 

 now be clearly traced. From twenty-two to thirty days after infection 

 the uterus of the parasite is filled with eggs. 



Mature specimens of the distome measure 5-12 mm in length 

 and 1-2,5 mrn » m breadth, the size apparently depending upon the 



