Fig:. 1716. Section through the 

 oyster along the line o of Fig. 171c 

 (enlarged twice), a', a", dorsal and 

 ventral branches of the anterior 

 aorta in section; br, artery to gills; 

 c, connective tissue; g, gills in sec- 

 tion; <;', internal cavities of thegills; 

 ge. egg-gland; I. i, cross-sections of 

 the intestinal tube; I, liver; mt, 

 mantle; sb, suprabranchial or water 

 spaces above the gills; st, stomach; 

 vc, vena cora. After Ryder. 



Fig. 171c. The oyster-drill. 

 (Natural size.) 



Fig. 171tt. Oyster. Gen, gland in which the eggs are formed; ov, oviduct, 

 from which the eggs are discharged; mus, adductor muscle; H, heart; mt, 

 mantle: P, palp; (?, gills. After Ryder. 



[To face page 832.] 



