PLATE 2. 



Fig. 7. Portion of cross section of proboscis, showing structure of lemniscus. 

 Sea-water and alcoliol, vora Ratli's mixture. X i^OO. 



Fig. 8. Part of Fig. 7 enlarged. X ca. 400. 



Figs. 9a, 96. Sections of a papilla perpendicular to its axis. Figure 9a represents 

 the more distal of tlie two sections, and sliows tlie form and position of tiie 

 three axial nuclei ; Figure 9b shows the two basal nuclei. The anterior face 

 of the papilla is directed toward the top of the plate in both cases. 

 Sea-water and alcohol, corrosive sublimate, iron liaematoxylin. 



Fig. 10. Portion of the cross section of an everted proboscis, showing one of the 

 eigliteen longitudinal nerves (n. Ig.) cut crosswise, tlie peripheral nerve plexus, 

 the union of tlie centripetal jirocesses from tlie sense cells witii the longitudinal 

 nerve (in tlie case of the third papilla from the upper margin of tlie Figure, 

 one of the two nerve fibres bends to tiie left when it enters the nerve plexus, tiie 

 otlier to the right), a radial nerve {n. r.) following tlie surface of the longitu- 

 dinal muscle (this is sketched in from an adjacent section), and another radial 

 nerve (n. r/) passing directly to tlie membrane which is immediately superficial 

 to the circular muscles. 



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

 X 145. 



Fig. 11. Papilla from a cross section of proboscis showing one of the basal and 

 one of the axial nuclei ; there are two large granulations in the basal nucleus. 

 The differentiation of the distal portion of the sense-cell is not well shown. 

 Sea-water and alcohol, sublimate-acetic, Kleinenberg's haematoxylin. X 460. 



