266 MARTIN F. WOODWARD. 



Fig. 12. — Dissection of the stomach with its spiral caecum, from above. 

 Fig. 13. — Dissection of the stomach of Trochus zizyphiuus, from 

 above. Enlarged. 



PLATE 14. 

 P. Beyrichii. 



Pig. 14. — Transverse section of the gill and branchial ganglion, showing 

 the gill-plates in surface view. Somewhat diagrammatic, x about 12. 



Pig. 15. — Transverse section of the gill, showing the circulation of the 

 blood in the gill-plates. Diagram constructed from sections, x about 13. 



Pig. 16. — Section across two gill-plates, taken along the line a b, Pig. 14. 

 X about 36. 



Pig. 17. — Section parallel to the last, but passing through the dorsal 

 junction of the gill-plates with the septum, x 170. 



Pig. 18. — Horizontal section across the outer margin of a gill-plate. X 

 500. 



Fig. 19. — Section through the branchial ganglion at the origin of the 

 branchial nerve. The ganglion is slightly contracted away from the connec- 

 tive tissue of the mantle, x 50. 



Fig. 20. — Section through the eye. x 60. 



Pig. 21. — Anterior portion of the nervous system from the left side of the 

 body viewed from within, showing the cerebral ganglion and its connections 

 with the pleuro-pedal cords, together with the origin of the subintestinal 

 nerve and the principal nerves to the head and side-walls of the anterior 

 part of the body. The first transverse pedal commissure is seen to be 

 formed from both the pleural and pedal cords, as also is the second pedal 

 nerve, x 2|. 



Fig. 22. — The corresponding portion of the nervous system from the right 

 side of the body, viewed Irom without. Drawn from a dissection with the 

 portion of the nerve-cells indicated diagrammatically from microtome 

 sections. X 6. 



PLATE 15. 



Pig. 23. — Dissection of the kidneys and pericardium, showing the extent 

 of the right kidney and its relation to the genital duct ; also the great venous 

 sinus. 



Pig. 24. — Dissection showing the relation of the left kidney to the peri 

 cardium. 



Fig. 25. — Semi-diagrammatic representation of the two kidneys, the peri- 

 cardium, reuo-pericardial canal, and genital duct. 



Fig. 26. — Schematic representation of the same. 



