Bull. U. S. B. F., 1919-20. 



Pl.nte XVIII. 



Fiii. I. — Seining fish from overflow water for infection with glochidia of mussels. 



Fig. 2—Sc 



... IV ,i;. iwr mussel propagation. Fig. =;. — Tr.ni- '■■■:■: . ; ■ .nx-ction tank. Foreman in 



boat is pounii;^' t!iet;loclii<lia iroma can into the t a n k . 



Fig. 4. — Sorting the fish for infection with glochidia. 



