208 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY. 



Fig. 7. Larva of Lumhrironereis, showing the formation of the mouth and first 

 body segment (1) below the ciliated band. The two clusters of cells 

 above the upper border of the same, near the medial line, are the 

 beginnings of cephalic ganglia. (Ventral view.) 

 7". Lateral view of a larva a little younger than the last. 



8. Larval Liunhrkonereis older than that shown in Fig. 7. 



9. Still more mature larva of the same, with the rudiments of a second (2) 

 and third (3) body segment. 



10. The same larva still more mature. 



n. Larva with three well-defined parapodia and rudiments of two segments 

 posterior to tUc last. 



12. A more mature larva with extended sette and well-developed jaws. 



13. The oldest form of the larval series referred to Lumhriconereis possessing 



seven pairs of seta;, the most anterior of which are doubled, while 

 the immature forms of new spines can be seen in the more posterior 

 segments. 



PLATE VIII. 



Lumbriconereis, Nectonema, and Unknown Genus. 



a. Anus. 



cp. Ciliated pits on the sides of the head. 



is. Immature setae at the base of those already formed in the body walls. 

 /. Lateral hnes. 

 / /. Lower jaw. 



sg. Division between two segments. 

 uj. Upper jaw. 

 ii\ Segmental orifice. 

 M' h. Bod^' walls. 



1, 2, 3, 4, in Fig. 3", articulations which together form the lower jaw. Of these 

 No. 1 is anterior. 



Fig. 1. Seta; and muscular attachments of the same in Zy((?n6r/co«cceis' larva. (The 



spine is represented as retracted.) 

 " 2. The same, extended. 



" 3. Larval Lumhriconereis with three parapodia. 

 " 4-10. Nectonema agilis Verr. 

 " 4. The adult Nectonema. 

 " 5. Enlarged view of the head of the same. 

 " 0. The head from dorsal side. 



" 7. Clear space witli contained cells (ova ?) in the head. 

 " 8. The same from dorsal side. 

 " 9. Magnified view of a section of the lateral line, destitute of lateral spines 



and "connecting web." These last structures were not found in this 



specimen. 

 " 10. Posterior end of the body ( ? ?). 

 " 11. Cephalotrix linearis (young). 



" 12-14. Three larval stages in the development of a mesotrochal Annelid, 

 probably Telejisnvfis or Phi/Iloclialojderus. (Younger than those 

 figured in PI. III. See text.) 



