BuLi,. U. S. B. F. 1912. 



Plate LIX. 



Fig. 12. — Salvelinns fontinalis in sac stage, hatched a few days; showing relation of th.vroid follicles to invagination 

 which becomes jugular pit. X86. 







l-it;. 1.^. — Iliook trijut J'r\ sliowiiiK' early thyroid follicles coiitaiiiiiiK •.■olluid material. XS6. 



