134 

 Plate V. 



Fig. 16. Diagram of vessels of ctenidiiim. 



Fig. IT. Arteries of lips and labial palps. Nat. size. 



Fig. 18. Part of veuous system of P. maximus, from 



injections. 

 Fig. 19. Ventricle and anterior aorta. 

 Fig. 20. Trans, section (diagram.) of ctenidium lliroiigli 



prin. filaments, showing course of blood, x 4. 

 Fig. 21. Section of ctenidium, transverse to filaments, at 



level of top of ascending filaments. x 130. 



Plate YI. 



Fig. 22. Section of ctenidium trans, to filaments, near 

 free margin, showing both demibrauchs with 

 interlamellar junctions. x 110. 



Fig. 23. Trans, section of principal and four ordinary 

 filaments, near base, showing respiratory 

 expansion. x 480. 



Fig. 24. Section of respiratory expansion of prin. 

 filament in same plane as ctenidium. x 10. 



Fig. 25. liespir. expansion of a principal filament, x 20. 



Fig. 26. General view of nervous system {P. maximus). 



Fig. 27. Cerebro-pleural and pedal ganglia. 



Fig. 28. Visceral ganglia (P. maximus), showing 

 osphradial ganglia and chief nerve trunks. 



Plate VII. 



Fig. 29. Longitudinal section of eye (P. maximus). 



X 150. 

 Fig. 30. Retinophorae, with rods and ganglionic cell 



layers (semi-diagram.). 

 Fig. 31. Cells of outer ganglionic layer. Zeiss apo. 1"5, 



with comp. oc. 4. 



