On the Young Stages of a few Annelids. 341 



Fig. 7. Stage in which the anterior disk is diminishing in] size and 

 becoming slightly elongated ; seen from the dorsal side. 



Fig. 8. Head of Nareda in stage of figure 7 ; seen from the mouth 

 side. 



Fig. 9. Older stage than figure 8 ; the rings are farther apart, the pig- 

 ment spots larger, the head has become greatly elongated, and the ten- 

 tacles are more prominent ; seen from the dorsal side. 



Fig. 10. Older than figure 9, the pigment spots have become quite 

 small, and the vibratile rings are much reduced ; seen from the dorsal side. 



Fig. 11. Somewhat more advanced than figure 10, the anterior disk 

 has lost its prominence, the vibratile cilia have nearly disappeared, the 

 stomach has become convoluted, the pigment cells are scarcely percepti- 

 ble, and the articulations quite indistinct ; seen in profile, very sluggish 

 in its movements, about one-fourth of an inch long. 



Fig. 12. Head of specimen slightly older than figure 11 ; seen in 

 profile. 



Fig. 13. The same seen from the dorsal side; the tentacles are con- 

 tracting. 



Fig. 14. Young Nareda, which has lost almost all trace of the tenta- 

 cles of the head, about half an inch long. 



Fig. 15. Head of a somewhat older specimen. 



Fig. 16. The same as figure 15 ; seen in profile. 



Fig. 17. The head of a Nareda which has become less wide than the 

 body ; about five months older than figure 4. 



Fig. 18. Portion of string of eggs of Spirorbis. 



Fig. 19. Young Terebella fulgida Ag., showing the order of de- 

 velopment of the tentacles t„ t 5 ; and the concretionary lime capsules 

 y, greatly magnified. 



Fig. 19a. Stiff bristles of the rings; magnified. 



Fig. 20. Young Spirorbis soon after its escape from the egg, having 

 only one tentacle developed on the right, t t . 



Fig. 21. Somewhat more advanced than the preceding figure, show- 

 ing first trace of opercular tentacle. 



Fig. 22. Young Spirorbis having three pairs of bristles, somewhat 

 older than the preceding stage. 



Fig. 23. The anterior extremity of a specimen more advanced than 

 fig. 22, showing the first trace of bifurcation of the tentacles. 



