Bull. U. S. B. F. 1912. 



Plate LVIII. 



J ■ 

 4 



ah-' 



11 



Fig. 5. — Redrawn from Maurer. 18S6. Thyroid of a trout 20 cm. long:; shown in its rel.ition to the branchial arteries, 

 seen from the ventral side. 



Fifi. 6. — Redrawn from Maurer. Median section to show distribution of thyroid about the ventral aorta in a trout 2. .5 

 cm. lone:. 



Fici. 7. — Redrawn from Maurer. Cross section of the head of a trout embryo of 30 days, showing earliest evagriuation 

 of pharyngeal epithelium to form the thyroid. 



Fi(:;.S. — Redrawn from Maurer. Median section through head of trout embryo of 35 days. Primary thyroid vesicle 

 (/) still attached to parent epithelium by pedicle. 



Fir,. 9, — Redrawn from Maurer. Cross section of a trout enil)r\o of 35 days. Primary thyroid vesicle Kt) sei>arated frotn 

 parent epitlielium. 



\'\<',. 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 ventral to the aorta. 



Fk;. 11. — Drawing show^ing gro.ss appearance of jugular pit from below. 



