Butx. U. S. B. F., 1923-24. (Doc. 963.) 
Fig. 1 .—Side view of a mussel immediately after leaving the cyst on the gill of the fish. About 
0.2 mm. long. A A, anterior adductor; PA, posterior adductor; F, foot; G, papillae of develop- 
ing inner gill; M, mantle; IP, inner palp; OP, outer palp; Mo, mouth; St, stomach; ltd, 
intestine. (Adapted from Herbers.) 
