PLATE 4. 



Figs. 21-23, 25, 27, 29, 30. Longitudinal sections of papillae from cross sections 

 of proboscis. 



Figs. 21-23, 25, 29. Preparations made by use of chloroform, methylen blue, 

 Bethe's ammonium molybdate for invertebrates. 



Figs. 24, 30. Preparations made by use of sea-water and alcohol, sublimate- 

 acetic, Kleinenberg's haematoxylin. 



Fig. 21. Three sensory cells, two showing peripheral fibres and terminations. 

 X 715. 



Fig. 22. Papilla showing a row of axial vacuoles. 



Sea-water and alcohol, Miiller's fluid, Beale's ammonia carmine. 



Fig. 23. The nuclei of the two sensory cells distinguishable from the cell body 

 by their deeper stain. Peripheral and proximal fibres stained. X 710. 



Fig. 24. Basal nucleus of a papilla showing a large single nucleolus. X 070. 



Fig. 25. Highly vacuolated papilla, fibrils and discs of the sensory termination 

 stained blue, the deep ends of each of the sensory cells prolonged into a few 

 processes, which unite to form the single nerve fibre. X 700. 



Fig. 20. Cross section of a small papilla, showing a nucleolus in each basal 

 nucleus. 



Sea-water and alcohol, vom Rath's mixture. X 680. 



Fig. 27. Papilla showing one of the basal nuclei with large nucleolus, and the 

 passage of connective-tissue fibrils into the papilla. 

 Sea-water and alcohol, vom Rath's mixture. 



Fig. 28. Papilla from sagittal section of proboscis, showing three axial nuclei 

 and two basal nuclei. 



Sea-water and alcohol, sublimate, iron haematoxylin. 



Fig. 29. Papilla from cross section of proboscis, showing numerous small 

 vacuoles, fibrils and discs of sensory termination. The basal end of each sen- 

 sory cell is prolonged into a slender nerve fibre. X 730. 



" Figs. 30a-30<7. Four successive sections from a single papilla. 



Fig. 306 shows one of the basal nuclei ; Fig. 30c, the other basal nucleus and 

 the two axial nuclei. 



In the region of the apex of the papilla, there is an interruption in the cortical 

 layer of finely granular substance, not well shown, and the region is traversed 

 by fine fibres. X 585. 



Fig. 31. Fibrils from the peripheral termination of a sensory cell. 



