83 



Fig. 29. Part of a section through the shell, passing 

 vertically to the shell surface and perpendicu- 

 lar to a line of growth. X about 25. 



Fig. 30. A schematic representation of the course of the 

 principal blood vessels and channels as seen 

 from the right side. 



Plate VI. 



Fig. 31. Dissection of a cockle from the ventral side, to 

 show the visceral ganglion and nerves. Only 

 the portion of the body behind the viscero-pedal 

 mass is shown. The fused portion of the inner 

 lamellae of the two internal branchiae is cut 

 through in the middle line, and the septum 

 between the siphons and the horizontal shelf 

 continuing this forward are cut likewise. X 

 about 2 diam. 



Fig. 32. Dissection to show the right cerebral ganglion 

 and surrounding parts. The extremity of the 

 anterior adductor has been cut away and the 

 muscle separated slightly from the anterior 

 wall of the viscero-pedal mass. The right 

 labial palps are mostly removed. X 4 diam. 



Fig. 33. Dissection of the proximal limb of the viscero- 

 pedal mass from its anterior margin to show 

 the pedal ganglion and nerves. The anterior 

 body- wall and the underlying muscles and geni- 

 tal gland tubules have been removed. X 3. 



Fig. 34. The otocyst of the right side in longitudinal 

 section. Zeiss apo. 1"5 mm., compens. oc. 4. 



Fig. 35. Section through an ovarian egg. X about 200 

 diam. 



