PLATE XIII. 



Fig. 



1. Structure of the stylet-region of the proboscis of Prosorhochmus Claparedii. Degeneration 



of the marginal sacs has ensued from long confinement. X 90 diam. 



2. Aspect of the developing proboscis (a) of Tetrastemma melanocephala, about the fifth day 



after the removal of the original organ. X 55 diam. 



3. Structure of the stylet-region of a developing proboscis of the same species. /, canal, which 



by-and-by is occupied by the central stylet. The organ is contracted. X 350 diam. 



4. Central stylet and basal apparatus with radiating fibres in Tetrastemma vermicula. X 350 



diam. 



5. Stylet- region of the proboscis of T. Candida, with the ejaculatory duct pressed to the left 



side. The marginal stylet-sacs are out of focus. X 210 diam. 



6. Central stylet and basal apparatus of a small specimen of the same species. X 420 diam. 



7. Structure of the stylet-region in Tetrastemma dorsalis, somewhat contracted, with the floor 



of the anterior chamber pouted forward, and the reservoir shortened in its antero- 

 posterior diameter. X 210 diam. 



8. Stylets of the same species, a, central stylet; b, stylet from a marginal sac. X 700 diam. 



c, central stylet and its basal granular apparatus. X 420 diam. 



9. Stylets of Tetrastemma flavida. a, central stylet; b, stylet from a marginal sac. X 700 



diam. c, central stylet and its basal apparatus. X 420 diam. 



10. Superficial structure of the stylet- and reservoir-regions of A. lactijioreus. Considerably 



magnified. 



11. Isolated marginal stylet-sac of the same species, a, fibres which probably act as constrictors 



of the aperture of the duct. The laminated arrangement of the calcareous layers of the 

 stylets is indicated in this figure. X 350 diam. 



12. Stylet-region of the proboscis of a young animal of the same species, illustrating the first 



appearance of the stylets and the development of the parts. The organ is drawn as it 

 bulged from a wound in the body- wall of the specimen. X 700 diam. 



13. Stylet-region of a young A. lactijioreus, some weeks older than that represented in the pre- 



vious figure. X 350 diam. 



14. Proboscis of an adult of the same species, gently but completely extruded under chloroform, 



so as to render the central stylet prominent. X 55 diam. 



15. Transverse section of the contracted reservoir-region of the proboscis of the same species, 



showing the complex spiral arrangement of the fibres. The organ is cut towards its 

 posterior end. X 55 diam. 



16. Transverse section of the posterior chamber of the proboscis in a large example of the same 



species. X 90 diam. 



17. Structure of the stylet-region in a developing proboscis of Nemertes gracilis. X 350 diam. 



18. Central stylet and its basal apparatus in the same species, turned round so as to demon- 



strate the curve of both. X 100 diam. 



19. Proboscis of Amphiporus pulcher treated as in fig. 14. X 55 diam. 



20. Fragment of the oesophageal region of the digestive tract from a living A. lactijioreus. 



a, inner edge of ciliated fold ; b } sulcus between two folds. X 350 diam. 



