PLATE L 



1. Tornaria seen in profile; n. s. about 2 mBU 



2. Tornaria seen from ventral side ; n. s. 2 mm * 



3. Tornaria, seen from dorsal side ; n. s. about 2 mm - 



4. 





12. 



13. 



16. 

 17. 



Part of the cesophagus in profile, to show the commencement of the gills as a thickening of the walls on the 

 dorsal side, from a Tornaria somewhat younger than Fig. 1. 



5. (Esophagus of Tornaria, seen in profi] 



Fig. L 



5". (Esophagus somewhat more advanced, s< 



6. Somewhat more advanced than Fig. 5°, 



7. (Esophagus seen from the mouth side, al 



8. (Esophagus considerably more advanced 



9. (Esophagus, with gills, somewhat more a 



10. (Esophagus seen from the mouth side, al 



1 1. (Esophagus seen in profile, same state of 



Part of Tornaria, seen from the dorsal side, to show the relative position of the oesophagus, water-system, 

 heart, and gills, to the digestive cavity. This is taken at about the time when Tornaria changes into 

 Balanoglossus. 



The water-system in profile, in a young Tornaria. 



14. The same 



15. Water-svs 



w 



Water-system and heart of an old Tornaria, seen from the dorsal side. 



Posterior extremity of the stomach of Tornaria, to show the position of the upper and lower lappets, first 



The 



formed as diverticula of the stomach, seen in profile. 



