How to obtain it. 223 



sealed vessel, but it will not grow in the open air. When the 

 water is low in our rivers and fish lie long in the pools, it often 

 happens that the " fungus " assumes an epidemic form. Therefore 

 if we can increase the supply of water, by producing an artificial 

 spate, the fish are helped to reach the sea, and as sea water has 

 been ascertained to be fatal to it, the benefit is apparent. 



Saprolegnia is a cryptogamic plant, belonging to the group 

 Thallophytes, and it occupies a position in that group between 

 Siphonece of the Alga* and Phycomycetes of the Fungi. At one 

 time it was a disputed point whether it belonged to the animal or 

 vegetable kingdom, but there is now, I think, no doubt about 

 that. The only doubt that remains seems to be its exact position 

 as a cryptogam. When seen upon a salmon or a trout it has a 

 woolly appearance, and often occurs in patches the size of a 

 shilling or a half-crown. Sometimes it covers the whole of the 

 head of a fish, whilst in others it takes possession of the J;ail or of 

 the back, or grows in a small tuft from one or more of the fins. 



If we examine this woolly-looking mass through a strong 

 magnifying glass, we shall find that it consists, first of all, of a 

 matted-looking mass of filaments, lying comparatively flat upon 

 the body of the fish. This practically constitutes the root, and is 

 known as the mycelium. From this root, or myceliu:/i, rise a 

 multitude of filaments or stems, called hyphce, each one of which 

 consists of a hollow tube, and a great many of these tubes have 

 their terminations enlarged, and assume a somewhat club-shaped 

 form. This club-shaped vessel is a zoosporangium, and is found 

 on examination to be full of minute seeds or zoospores. These, 

 when ripe, are rapidly expelled from the zoosporangmm, or seed 

 vessel, and have the means of locomotion, moving about in the 

 water by means of their two cilia, which may almost be likened to 

 a pair of oars. 



Until the plant is ripe, and begins to give off its seeds, there 

 is not much danger of infection, and in its earlier stages it is 

 easily destroyed by permanganate of potash or carbolic acid. To 

 kill and bury every fish that can be got out of a river with any 

 fungus upon it is a great mistake, and yet I have known this to be 

 done. A great many of the fish so destroyed might have been! 

 saved, the fungus upon them not being at the time particularly 



