PLATE XCVIII. 





BULL. U. S. B. F. 1912. 



FIG. 98. Marked hyperplasia domesticated brook trout used as control for figure 99. Fish 1070, table ix. X86. 



FIG. 99. 'Fish from same lot treated by addinsr in continuous concentration potassium iodide in the water 1 : 5, 000. 000. 

 Marked regression of hyperplasia at the end of 27 days. Fish 1069, table ix. X86, 



