356 Diseases of Fishes 



come to maturity. Also, as it is nature's plan that the adult 

 lampreys die after spawning once, we are convinced that death 

 would ensue without the attack of the fungus; and in fact this 

 is to be regarded as a resultant of those causes that produce 

 death rather than the immediate cause of it. Its only natural 

 remedy is to be found in the depths of the lake (450 feet) where 

 there is a uniform or constant temperature of about 39 Fahr., 

 and where the light of the noon-day sun penetrates with an 

 intensity only about equal to starlight on land on a clear but 

 moonless night. 



" As light and heat are essential to the development of the 

 fungus, which is a plant growth and properly called a water 

 mold, and as their intensity is so greatly diminished in the 

 depth of the lake, it is probable that if creatures thus attacked 

 should reach this depth they might here find relief if their 

 physical condition were otherwise strong enough to recuperate. 

 However, we have recently observed a distinct tendency on 

 the part of fungus-covered fishes to keep in the shallower, and 

 consequently warmer, parts of the water, and this of course 

 results in the more rapid growth of the sarcophytic plant, and 

 the death of the fishes is thus hastened. 



" All kinds of fishes and fish-eggs are subject to the at- 

 tacks of such fungus, especially after having been even slightly 

 scratched or injured. As a consequence, the lamprey attacks 

 on fishes cause wounds that often become the seat of a slowly 

 spreading but fatal fungus. We have seen many nests of the 

 bullhead, or horned pout (Ameiurus nebulosus], with all the 

 eggs thus destroyed, and we have found scores of fishes of vari- 

 ous kinds thus killed or dying. It is well known that in many 

 rivers this is the apparent cause of great m rtality among adult 

 salmon. Yet we really doubt if it ever attacks uninjured fishes 

 that are in good strong physical condition which have not at 

 least had the slime rubbed from them when captured. It is 

 contagious, not only being conveyed from one infested fish to 

 another, but from dead flies to fishes." (For a further discus- 

 sion of this subject see an interesting and valuable Manual of 

 Fish Culture, by the U. S. Fish Commission, 1897.) 



Earthquakes. Occasionally an earthquake has been known 

 to kill sea-fishes in large numbers. The Albatross obtained 



