Report U. S. F, C. 1897. (To face page 340.) 



Plate VIII. 



Fig. 1. View of right side of embryo about G days old. hi, mouth; r, veut; I, right lobe of liver; vl, velum. 



Fig. 2. Older larva of European oyster, Ostrea lurida. L, shell; h. hinge; rs and rj, retractor muscles of 

 the velum, vl; s, stomach; i, intestine; am, larval adductor muscle; b, body cavity. Other letters as in 

 the preceding. 



Fig. 3. Attached spat of Ostrea virginiana. S, shell of spat with larval shell, L, at the beak or umbo; p, 

 palps; 0, gills; c, diagrammatic representation of a single row of cillia extending from the mantle border to 

 the mouth m; r, radiating muscle fibres of mantle; f, rudimentary tentacles of mantle border; M, perma- 

 nent adductor nmscle; C, cloaca: ve and aw, ventricle and auricle of the heart; ij, posterior extremity of 

 the gills and junction of the mantle folds. Other figures as above. Compare this figure with PI. I, fig. 1. 



Fig. 1 after W. K. Brooks. Fig. 2 after Thomas H. Huxley. Fig. 3 after John A. Ryder. 



