208 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY. 



Fig. 7. Larva of Lumbriconereis, showing tlie formation of the moutli 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 Lumhrkonereis older than that shown in Fig. 7. 



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

 and tliird (3) body segment. 



" 10. Tiie same larva still more mature. 



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

 posterior to tlie last. 



" 12. A more mature larva witli extended setaj and well-developed jaws. 



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

 seven pairs of setffi, the most anterior of which are doubled, while 

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

 segments. 



PLATE Vin. 



Lumbriconereis, Nectonema, and Unknown Genus. 



a. Anus. 



cp. Ciliated pits on the sides of the head. 



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

 /. Lateral lines. 

 / /. Lower jaw. 



s f/. Division between two segments. 

 u J. Upper jaw. 

 w. Segmental orifice. 

 IV b. Bod}' walls. 



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

 No. 1 is anterior. 



Fig. 1. SetEB and muscular attachments of the same in L«m6r/coHe?'e2s larva. (The 



spine is represented as retracted.) 

 " 2. The same, extended. 



" 3. Larval Lumbriconereis 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 with 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. Cephulotrix linearis (young). 



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

 probably Telrpsavfis or Pliij!/oc/uEloj>terns. (Younger than those 

 figured in PI. IIL See te.xt.) 



