Parasites, Diseases and Enemies. 251 



EXTERNAL PARASITES. 



A deadly parasite is the fungus which is called 

 Saprolegnia ferax by scientists, although the micro- 

 scope shows variations which may be different species. 

 Of this I am not qualified to speak. It appears to be 

 nearly the same on the fish as on the egg, a woolly or 

 cottony growth. We often see it on dead flies in water, 

 and the fact is that spores of this fungus are every- 

 where in the water, only awaiting a suitable field to 

 grow in, just as spores of mould in the air will find a 

 good field in a pair of damp boots in a dark closet, 

 while spores which fall on dry boots will not germi- 

 nate. An abrasion on the skin of a fish, a bruise or 

 other injury, is an inviting field for fungus, but a clean 

 cut does not seem to be so favorable for its growth. 



A favorite spot for this fungus to germinate is where 

 the protecting slime has been removed from a fish, 

 and this slime is readily removed by a dry hand, hence 

 in the chapter on taking trout eggs I insist on the 

 hands being wet before the trout is touched. It is not 

 uncommon to find a dead fish with the print of a 

 thumb on one side of its back and of the fingers on the 

 other, where some kind angler has returned a fish to 

 the water after handling it, in ignorance that he signed 

 its death warrant when he touched it with a dry hand. 

 You may take a fresh-water fish of any kind and lay it 

 in a dry towel, smoothing the towel gently about it and 

 then return the fish to the water, when it will swim off 

 apparently unharmed ; about a week afterward the fish 

 will appear to have a bloom, like that of a ripe purple 

 grape or plum upon it, and then comes the "cottony 



