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



PLATE LXIII. 



Fui. 19. Domesticated Scotch sea trout fingrerling-; normal thyroid structure. X86. 



^V &l 



m ; 







. . . - 



" j.V 



KIG. 20. Dotnesticated Scotch sea trout fmgrerliiiK: same hatchery as above, showing simple hyperplasia, increased 

 number of thyroid follicles; epithelium high cuboidal and low columnar; colloid diminished. X86. 



