Bull. U. S. B. F. 1912. 
Plate LIX. 
Fig. 12 . — Salvelinus fontinalis in sac stage, hatched a few days; showing relation of thyroid follicles to invagination 
which becomes jugular pit. X86. 
1 #^ 
'iv' 
Fux 13. — Hrook trout fry sliowiiigf early tliyroid follicles coiitainiiiK’ colloid material. X86. 
