Bull. U. S. B. F. 191 2. 



Plate LVIII. 



11 



Fig. 5. — Redrawn from Maurer. 1886. Thyroid of a trout 2(i cm. lon^; showni in its relation to the branchial arterie.s. 

 seen from the ventral side. 



Fig. 6. — Redrawn from :Maitrer. Median section to show distribution of thyroid about the ventral aorta in a tront 2.5 

 cm. long. 



Fig. 7. — Redrawn from Maurer. Cross section of the head of a trout embryo of 30 days, showing ear'iest evagination 

 of pharyngeal epithelium to forni the thyroid. 



Fig. 8. — Redrawn from Maurer. Median section through head of trout embryo of 35 days. Primary thyroid vesicle 

 (/) still attached to parent epithelium by pedicle. 



Fig. 9. — Redrawn from Maurer. Cross section of a trout embryo of 35 days. Primary thyroid vesicle (/) separated from 

 parent epithelium. 



Fig. 10. — Redrawn from Maurer. Median section through head of trout embryo of 41 days. Compared with figure S, it 

 shows that the elongated primary thyroid vesicle (/) has moved backward and now lies ventnil to the aorta. 



Fk;. 11. — Drawing showing grcss appearance of jugular pit from below. 



