PLATE II. 



Fig. 15. Transverse section of epithelium of tentacular fold to show the leucocytes 

 in situ. Hamann's carmine. Zeiss 1. E. X 500. 



" 16-18. Sense papillae from anterior papillate zone of introvert. 



" 16. Tangential section through a single papilla. Hamann's carmine. Zeiss 

 1. D. X 300. 



" 17. Transverse section. Apical area retracted. Hamann's carmine. Zeiss 

 1. D. X 330. 



" 18. Transverse section. Papilla fully expanded. Orth's picro-litho-carmine. 

 Zeiss 1. D. X 220. 



" 19. Lateral sagittal section of brain at point of departure of the anterior com- 

 missure from the central fibrous mass. Plane of section indicated on 

 Figure 22 by dotted line " 19." Mayer's cochineal. Zeiss 1. A. X 50. 



" 20. Median sagittal section of brain. Plane of section indicated on Figure 

 22. Mayer's cochineal. Zeiss 1. A. X 50. 



" 21. Cells of tentacular epithelium isolated by maceration ; a, c, and e, sensory, 

 b, d, and/, filamentous cells. Zeiss apochr. 4 mm. Oc. 8. X 725. 



" 22. Central nervous system. Composite figure from maceration preparations 

 controlled by serial sections. The splanchnic nerve (n. spl.) should 

 project forward under the brain. For the sake of clearness it is repre- 

 sented as if turned posteriad ; * denotes inferior muscular branch (?). 

 The numbers denote the planes of sections represented in Figures 19, 

 20, 24, and 25. X 8 (about). 



