Bull. U. S. B. F., 1921- 



Fig. 60. — A crate of improved pattern showing outer screens of 1-inch mesh and inner detachable screens of copper 

 cloth, one of which is completely removed and the other turned in to show manner of insertion. Infected fish are 

 held in the crates until the parasitic mussels are shed. The copper cloth prevents the escape of the mussels in the early 

 minute stages. 



Fig. 61. — Concrete ponds used for mussel culture experiments. In the dry pond on the left is shown the method ol 

 dividing into smaller units by means of screens. Bridges are shown over the two ponds on the right These furnish 

 shade lor the fish and prevent their jumping over the screens as well as serving the purpose of bridges for the operators 

 when seining the fish. Earth ponds and shed-covered troughs appear in the background. 



