-3 



12 



13 



10 



FIG. 168. View of Holothuria tubulosa somewhat diminished. The animal 

 is opened along the left dorsal interradius and the viscera are exposed. 

 After Ludwig. 



1. Tentacles. 2. Ampullae of tentacles. 3. Water-vascular ring. 



4. Polian vesicle. 5. Stone-canals. 6. Radial water-vessel. 



7. Eadial longitudinal muscle partly cut away. 8. Reproductive 



organ. 9. Alimentary canal. 10. Cloaca. 11. Respiratory trees. 

 12. Ventral " blood "-vessel. 13. Dorsal " blood-plexus." 



