114 



Fig. 7. Section through part of the body passing through 

 the anterior part of the renal organ parallel to 

 the branchial filaments. X 12 diam. 



Fig. 8. Blood corpuscles from one of the branchial 

 vessels. Zeiss apo. 1'5, compens. oc. 4. 



Fig. 9. Transverse section through a renal tubule. X 

 500 diam. 



Fig. 10. The left valve of the shell, seen from the inside. 

 Nat. size. 



Plate III. 



Fig. 11. Section through the middle part of the proximal 

 limb of the viscero-pedal mass, transverse to 

 the axis of the latter, and in the horizontal 

 plane of the body. X 7 diam. 



Fig. 12. Transverse section through the straight portion 

 of the intestine. X about 50 diam. 



Fig. 13. Transverse section through the spiral portion of 

 the intestine. X 50 diam. 



Fig. 14. Transverse section of the rectum near the anus. 

 X 50. 



Fig. 15. Section through part of the digestive gland, 

 showing the transition from ciliated to glandu- 

 lar epithelium. X 50 diam. 



Fig. 16. Transverse section of a secreting alveolus from 

 the digestive gland. Zeiss apo. 1"5, compens. 

 oc. 4. 



Fig. 17. Transverse section of part of a bile duct. X 

 500 diam. 



Fig. 18. Vertical section through part of the stomach 

 wall. X 280 diam. 



