PLATE 1. 



Fig. 1. Longitudinal section of the everted proboscis showing: (1) the sheath of 

 the proboscis; (2) the bearer of the jaws and its subdivision; and (3) the 

 lemniscus (Imn.), which marks the boundary between (1) and (2). 



Narcotized in a mixture of sea-water and alcohol; fixed in Muller's fluid; 

 stained with Beale's ammonia carmine. X circa 11. 



Fig. 2. Cross section of the partially everted proboscis in the region of the four 

 lemnisci (Imn.), showing, among other things, a diagrammatic representation 

 of the papillae and the connection of their sensory cells with the circular and 

 the longitudinal nerves, and also the nerve fibre (n. r.') passing to the membrane 

 which invests the circular muscles. 



Chloroform, methylen blue, Bethe's ammonium molybdate for invertebrates. 

 X 14.5. 



Fig. 3. Papilla from a cross section of the proboscis, showing two "basal" and 

 three " axial " cell nuclei. 



Sea-water and alcohol, sublimate-acetic, Kleinenberg's haematoxylin. X 675. 



Fig. 4. Longitudinal section of a papilla, from a cross section of the proboscis, 

 showing the two axial nuclei and one of the two basal nuclei, also fibrous struc- 

 tures entering the base of the papilla. Treatment the same as in Fig. 3. 

 X 585. 



Fig. 5. Longitudinal section of a papilla, from a sagittal section of the proboscis, 

 showing two sensory axial cells with peripheral sensory termination and 

 prolongation of the basal end of each into a slender nerve fibre. 



Chloroform, methylen blue, Bethe's ammonium molybdate for invertebrates. 

 X 650. 



Fig. 6. Papilla from cross section of proboscis viewed from behind, showing the 



corrugations of the cuticula on the posterior face of the papilla, and in optical 



, section the two zones of living substance together with one of the basal nuclei. 



Sea-water and alcohol, sublimate-acetic, Kleinenberg's haematoxylin. X 585. 



