222 



How to obtain it. 



eighths of an inch in diameter. The common one is Argulus 

 foliaceus. We have found them on gudgeon frequently, and also 

 on trout and pike. They swim freely and adhere to their host by 

 means of powerful suckers, and leave a bare patch wherever they 

 have adhered, thus rendering the fish peculiarly liable to an attack 

 of fungus. A saline solution is the best remedy for this, and 

 probably for most fresh water parasites. 



Fig. 45. A rgulns folinceits, enlarged. 



Some of the worst parasites are the Entozoa or internal 

 worms, which scmetimes are found to be the cause of a considerable 

 fatality amongst fish. We have taken a tape worm over two feet 

 long out of a trout, as well as a dozen or so of small round- 

 pointed worms, probably Ammlaria. These may be introduced 

 with food as cysts, and then develop, but as they are built in 

 segments, and every joint or section may become another worm 

 if detached, it is highly desirable that no domestic animal be 

 drowned in a fish pond, or in a stream leading to one. Dogs are 

 frequently troubled with worms, and the drowning of a dog might 

 easily be the source of introduction, eventually causing serious 

 disaster amongst the fish inhabiting the water. 



Every one probably has heard of the parasite commonly 

 known by the name of "fungus," or "salmon disease." It is 

 known to fish culturists as Saprohgnia ferax, but there are other 

 species, probably which will attack fish. There is another 

 (Leptomitus davatus) which attacks dead fish and decaying meat, 



but the Saprolegnia will grow on either the living or the dead. It 



. " - *^- t i 



grows in the water, and it can be grown in air in a hermetically 



