Ward. — Sipunculus. 



PLATE I. 



Fig. 1. Anterior half of the introvert. The base of the figure corresponds to the 



middle of the posterior papillate zone. The slight contraction at the 



centre of the zona levis is not usually found. Camera outline. Simple 



microscope. X 3. 

 " 2. Anterior aspect of tentacular fold. The figure is diagrammatic only to 



the extent that secondary folds are omitted. Camera outline. Simple 



microscope. X 4. 

 " 3. Sagittal section of introvert. Diagrammatic in regard to details. Simple 



microscope. X 8. 

 " 4. Longitudinal section of body wall of introvert in the anterior portion of 



the posterior papillate zone. Muscles diagrammatic. Bohmer's hsema- 



toxylin. Zeiss 3. A. X 98. 

 " 6. Transverse section of body wall at about the region indicated by the line 



gl." in Fig. 4. Hamann's carmine. Zeiss 1. D. X 370. 

 " 6-8. Sections of bicellular glands in the three dimensions of space. Kleinen- 



berg's haematoxylin. Zeiss apochr. 4 mm. Oc. 6. X 425. 

 " 6. Soon after the beginning of secretion. The membrane dividing the two 



cells Is shown at *. 

 " 7. At the period of greatest activity in secretion. 

 " 8. At the close of secretive activity. 

 " 9. Transverse section of duct of bicellular gland immediately below the 



cuticula. Zeiss apochr. 4 mm. Oc. 6. X 425. 

 " 10, 11. Longitudinal and transverse sections of bicellular glands to demon- 

 strate position of nuclei. Hamann's carmine. Zeiss apochr. 4 mm. 

 Oc 6. X 425. 

 " 12-14. Multicellular glands. Zeiss apochr. 4 mm. Oc. 6. X 400. 

 " 12. Longitudinal section. The duct is filled with a secreted material. Klei- 



nenberg's haematoxylin. 

 " 13. Transverse section. At the left centre of the section a cell has fallen out. 



Hamann's carmine. 

 " 14. Longitudinal section to demonstrate nuclei and connection of gland cells 



with nerve fibres. Mayer's cochineal. 



