PLATE 3. 



Figs. 12, 14, 15, 18, 19, 20. Preparations made hy use of chloroform, methylcn 

 blue, anil Bcthe's auinionium niolybdate for invertebrates. 



Figs. 13, 16, 17. Prepared by use of sea-water and alcohol, sublin.ate-acetic, 

 Kleinen berg's haematoxylin. 



Fig. 12. Papilla from cross section of proboscis, showing connective-tissue fibres 

 passing into tlie papilla; deep coloration of terminal fibrils; the nerve fibres 

 bending in opposite directions where they enter tlie nerve plexus. X 080. 



Fig. 13. Papilla from cross section of proboscis, sliowing corrugations of 

 posterior face of papilla, and the outline of one of tlie basal nuclei. X 460. 



Fig. 14. Papilla from sagittal section of proboscis; tlie two sensory (axial) 

 cells, tlieir peripheral terminations, and their proximal nerve-fibre prolonga- 

 tions stained blue. 



The nucleus of one of the sensory cells more deeply stained than the cell body. 

 Cuticula distended and detached from substance of the papilla by treatment. 

 X 710. 



Fig. 15. Papilla from cross section of proboscis, showing deeply stained axial 

 body, from wiiich a single peripheral, deeply stained process extends to tlie apex 

 of papilla, where it terminates in a specialized and stained area ; the contents of 

 the papilla in great part fibrous. X 1020. 



Fig. 10. Somewhat oblique cross sections of two papillae from a cross section of 

 the proboscis. In one papilla are two basal nuclei and a part of one of the 

 axial nuclei ; in the other the three axial nuclei cut crosswise. X 070. 



Fig. 17. Cross sections of two papillae from a cross section of proboscis. In one 

 are seen two axial nuclei, each surrounded with a clear area; in the other a 

 basal nucleus and portions of two axial (') nuclei. X 070. 



Fig. 18. Papilla from cross section of proboscis. The two sensory cells are 

 stained throngliout ; their distal prolongations iiave a more or less spiral course 

 and terminate in a cluster of discs at the apex of the i)apilla. Vacuoles large. 

 X 715. 



Fig. 19. Papilla from cross section of proboscis, showing that where the cen- 

 tripetal fibres from two sensory cells meet the nerve plexus, one bends to the 

 right, the other to the left. X 725. 



Fig. 20. Papilla from cross section of proboscis, showing the basal position of 

 the sensory cell body f?) ; the basal end of each sensory cell is prolonged into a 

 slender nerve fibre. X G82.5. 



