REARING THE YOUNG FRY. I97 



few fish and is not contagious. I know of no special 

 cause and no remedy. Green says the fish can be 

 sometimes saved by tapping the sac and letting out 

 the dropsical matter ; but I doubt it, and think the 

 disease is always fatal. 



5. Deformity at birth. Some trout are born with 

 curved spines, spiral spines, double heads, and with 

 bodies more or less imperfect. The proportion of 

 these to the whole is generally small, though the num- 

 ber of deformed spines will be made considerable by 

 careless hatching. Unless the deformity is slight, the 

 fish will not live long after feeding, although a double 

 fish, with two distinct vertebral columns and separate 

 tails, and united only at the sac, will survive for some 

 time. If the deformity is trifling, they sometimes live. 

 I have killed several grown-up trout with somewhat 

 bowed and crooked backs. Careful hatching is the 

 remedy for deformed spines, or rather the preventa- 

 tive. 



6. Fungus on the surface of the body. This cause 

 of mortality is distinct from fungus on the egg, as it 

 attaches itself to fish hatched from perfect eggs. The 

 fish usually get the fungus on them when quite young, 

 by rubbing it off the sides of the box or pond in which 

 they are confined. It sometimes floats down with the 

 water and gets in their gills. It is always fatal, and 

 usually very destructive. It cannot be too carefully 

 guarded against. There is no remedy for the disease 

 after it attacks the fish, unless it is salt water.* It can 

 be prevented only by shutting off any possibility of 



* See Appendix I. 



