Nos. 618-619] RESTOCKING INLAND WATERS 345 



worms that had crawled out of their cyst during the night. 

 If I had cared to do so I could have gathered several 

 hundred specimens during the day as they continued to 

 escape from the cysts. 



This observation answers one question, namely, that 

 these parasitic worms remain in the body of the perch 

 all winter, as the worms were in the same stage of ma- 

 turity as those taken in July, August and September. 

 It further suggests, also, that Clinostomum marginatum 

 may return to an aquatic habit directly from the body of 

 the fish. 



Guides and fishermen claim that perch are free from 

 "grubs" at certain seasons of the year, a belief which I 

 am unable to confirm. But if more extended studies show 

 that their belief is true, the method by means of which 

 the "grubs" leave the fish has been found. 



So far as we know, these parasites are mainly confined 

 to members of the bass and perch families, although a 

 few cases are on record of trout being infested with them. 

 Occasionally one finds a few bullheads that are "grubby." 

 In Lake Clear Lepomis gibbosus and the minnows are 

 largely infested by them. 



I can also confirm my observations (p. 11, '14) that fish 

 eating parasitized minnows are not themselves infected 

 through this avenue. One brook trout was found with 

 a partly digested minnow in its stomach. In the flesh 

 of the minnow a dead parasitic clinostomum was ob- 

 served. 



I would say that the number of fish harboring this 

 parasite in Lake Clear is on the increase. 



The following observations upon some larval stages in 

 Trematodes may help to start some one upon this prob- 

 lem without losing a season experimenting. 



During the past three years, I have frequently found 

 in the muscles of perch and pumpkin seeds minute cysts. 

 Each of these cysts contains a larval Trematode. 



The wall of the cyst is tough and easily "shells out" of 

 the muscles, but is not readily penetrated by the ordi- 



