206 BULLETIN OF THE 



Fig. G''. Serrated spine of parapodium. 



" 7. Larva of Nephthjs older tiian the last. View from the dorsal side. 



" 8. The same. View from the ventral side. 



" 9. Larva of Neplithijs in which the ceplialic tentacles have begun to form. 



" 10. The same. View from the dorsal side. 



" IL Still older larva. 



" 12. Oldest larva, of Ncjihi/iijs. 



" 12\ Head of the same. 



" 12''. Parapodium of fourth segment. 



" 13. Larva of Uarmoihoe (?). 



" 13*. The same seen from above. 



" 14. Youngest liiTva, iound of Lepidonotus scjuamatus. 



" 15. The same, more advanced in growth (lateral view). 



" 10. More advanced stage of Lepidonotus than the last (dorsal view). 



" 17. The same (ventral view). 



" 18. Telotrochal larva allied to the young of Pohjgordius. 



PLATE V. 



Pilidium (?) and Tornaria. 



a. Anterior end of the worm. 



CO. External opening of the cephalic sac. 



c s. Ceiihalic sac. 



dp. Dorsal pore. 



i. Invagination in the lateral wall of the larva. 



VI. Mouth. 



OR. ffisophagus. 



r. Half-absorbed remnant of the larva. 



s. Stomach. 



10 1. Water vascular system. 



Fig. 1. Youngest Nemertean larva with well-developed oesopliagus and stomach. 



" 2. Dorsal view of the same. 



" 3. Older larva with extended snout. 



" 4. Larva still older than the last. 



" 6. Dorsal view of the same. 



" 6. Older larva with lengthened proboscis. 



" 7. Larva just before the extrusion of the worm. 



" 8. Larva of the same age as that shown in Fig. 3, yet without cephalic sacs. 

 " 9, 10. Larva just before the birth of the contained Neujertean. 



" 11. Young worm just transformed from the larva. 



" 12. Dorsal view of the same. 



" 13. Side view of the last. 



" 14. An older Nemertean whicli probably developed from the last. 



" 14'. Proboscis, seen from below. 



" 14''. The same, from one side. 



" 15. Critical stage in the raetamorpliosis from the original larva. 



" IG. Youngest Tornaria found at Newport. 



" 17. Still more mature Tornaria, also from Newport. 



