Bull. U. S. B. F. iyi2. 



Plate LXIII. 



.■w 





Fig. 19. — Domesticatetl Scotcli sea trout tinj^erlinfi-; normal tIi>roid structure. XSb. 









Fig. 20. — Domesticated Scotch sea trout fingerliug: same liatchery as above, showing simple h>perplasia. increased 

 number of thyroid follicles: epithelium high cnboidal and low columnar: colloid diminished. XS6. 



