REARING THE YOUNG FRY. 195 



5. Deformity at birth. 



6. Fungus on the surface of the body. 



7. Constitutional weakness. 



8. Emaciation. 



9. Starvation. 



10. Ulcers on the head. 



11. Animal parasites. 



12. Fin disease. 



13. Black ophthalmia. 



14. Irritation of the optic nerve. 



15. Inflammation of the gills. 



1 6. Black gill fever. 



1 7. Fatty degeneration of the vitals. 



1 8. Spotted rash. 



19. Strangulation by food. 



20. Cannibalism, nibbling. 



21. Overheating. 



22. Suffocation. 



23. Paralysis. 



i. Fungus on the egg. This is the most insidious, 

 the most devastating, and the most obnoxious of all 

 the diseases of young trout, and the first in order of 

 the causes of death. It blights the embryo in the egg. 

 Once present in the water, it spreads unseen over all 

 the eggs, and is sooner or later fatal. The effect of 

 fungus has been already described in the chapter on 

 Hatching the Eggs, p. 127. We mention it here again 

 among diseases of trout fry, because it sometimes does 

 not kill the eggs, but causes them to produce prema- 

 turely a weakly young fish, which usually dies before 

 summer. 



