320 On the Young Stages of a few Annelids. 



says these sacs pass through the intestinal canal into the tuhe ; 

 this seems scarcely possible, but in whatever manner this may be 

 done, the strings of eggs rind their way whole from the sides ol 

 the alimentary canal to the cavity of the tube. 



As I shall have to refer constantly to the development of the 

 tentacles in Terebella, as observed by Milne Edwards, I give 

 here a short description of an identical mode of development in 

 one of our common species — the Terebella fulgida Agass* 

 The figure is taken at a time when there are but five ten- 

 tacles, and no signs of the branchiae ; these are only developed 

 much later, when there are no less than from sixteen to eight- 

 een tentacles, and are at that time short processes with very 

 simple bifurcations appearing at the extremity. In the con- 

 dition here figured, Fig. 19, our young Terebella closely resem- 

 bles Figure 24 of Milne Edwards, at the time when, as shown 

 by him, they are more closely allied to rapacious Annelids, 

 before they lose their embryonic characters, and acquire more 

 distinctly those of the adult. The eyes are still in prominent 

 clusters and not yet formed into a ring round the collar, as they 

 are arranged while gradually disappearing ; below them we 

 find on each side of the body the concretions (Fig. 19 y) first seen 

 in Annelids by Leuckartf and Mtiller,^ and also observed by 

 Claparede in the young of his Terebella conchilega. This is the 

 only point of importance in which the young of Terebella ful- 

 gida differ from those of Terebella nebulosa ; in each we find, as 

 in Figure 19, tentacles developing alternately on opposite sides, 

 in the order marked in the figure; the first ring having dorsal 

 setse, has also a row of hook-shaped bristles (Fig. 19 a ) found in 

 each ring nearly to the posterior extremity. This combination 

 is different from that observed by Claparede in T. conchilega, 

 where no such hook-shaped bristles were observed before the 



* Agassiz L. Studies in Annelids, in Proc. Boston Soc. Nat. Hist. iii. p. 191. 

 ■)• Leuckart u. Pagesstecher; in Archiv f. Anat. u. Phys. 1858. p. 591. 

 \ Mulleb Fritz ; in Archiv fur Naturg. 1861. L p. 46. 



