204 BULLETIN OF THE 



PLATE II. 



Spio, Aricidea, and Polygordiua. 



a. Anus. 



at. Tuft of cilia arising from tlie caudal extremity of the body on the dorsal side 

 of the vent. 



c. Cluster of cells near the anal pole of the larva. 

 cs. Ciliated pits. 



d. Cluster of cells which later concentrate into a cephalic ganglion. 



e. Funnel-shaped organ described by Hatschek. 



f. Flagellum. 



frs. Larger ciliated belt. 



i. Intestine. 



In. Lateral nerves. 



m. ]\Iouth. 



mp. Pigmented bodies on the lower lip. 



n. Kerve from apical ganglion to upper lip. 



0. Ocellus. 



ce. Oesophagus. 



p. Spherical bodies on rim of the disk. 



r. Characteristic pigment band on the dorsal region. 



s. Stomach. 



s rs. Smaller ciliated belt. 



«. Transparent projection on the dorsal side at the junction of anterior and pos- 

 terior body regions. 



vn. Ventral nerve, extending from the caudal end of the larva to the spherical 

 bodies foiind on the lower lips. 



Fig. 1. *S/)/o larva (dorsal view). 



" 2. More advanced larva of the same. 



" 3. Spio larva (side view). 



" 4. Aricidea larva (dorsal view). 



" 5. The same, with embryonic spines elevated. 



" G. Older larva of Aricidia. 



" 7. Youngest larva of Prionospio tenuis Verr. 



" 8. Posterior region of the last. 



" 9. Capite/la larva. 



" 10. Youngest " Loven's Larva" {Pohjfjordius). 



" 10''. The same, from above. 



" 11. Still older larva of the same. 



" 12. Older Loven's Larva. 



" 13. More advanced larva (side view). 



" 14. View of the same from above. 



" 15. Magnified portion of the rim of the last. 



" 16, 17. Pigmentation of posterior end of PoJijijordius larva (16, anus closed; 



17, cloacal wall extruded). 



" 18. Adult Pohjfjordius raised from the above larva. 



