No. 2.] DEVELOPMENT OF MARINE ANNELIDS. 26 1 



The prototroch and paratroch, before their actual disappear- 

 ance, undergo a marked degeneration. The cells shrink and 

 become filled with yellow gran- 

 ules, and within a compara- 

 tively short time all the ciliated 

 tracts on the surface and all 

 the mucous glands disappear. 

 These phenomena, together 

 with the fact that the glands 

 occur in the region of the 

 prototroch and paratroch, in- 

 dicate that they are correlated 

 physiologically with the cilia. ^^ 

 The problematic bodies also 

 partially collapse and then dis- 

 appear, and a median tentacle 

 is formed by an evagination 

 of the body-cavity just ven- 

 tral to the apical pole. Since 

 this appears before the ducts 

 of the mucous glands and the 

 problematic bodies have en- 

 tirely degenerated, it is a valu- 

 able means of orientation in 

 later stages (text Figs. XVII, 

 XVIII). 



Text Fig. XVIII shows the 

 large mouth, the position of brain, cord, eyes, nephridia, etc. 



?na?c 



Fig. XVIII. — Anifhitrite, ii days, optical sec- 

 tion: med.t., median tentacle; br., brain; 

 tnth., mouth; neph., nephridium; v.n., ven- 

 tral nerve cord; parapod., parapodia; St., seta 

 (dorsal); jj^.z/., set^ (ventral hooked); muse, 

 muscles of sets ; /, //, ///, etc., trunk 

 segments. 



B. CLYMENELLA TORQUATA verrill. 



Habits and cleavage. — The breeding habits of Clymenella 

 torqttata in the vicinity of Woods Holl are very different from 

 those of Amphitrite. While the latter may be found breeding 

 at any time during the summer, but never in great abundance, 

 the breeding season of Clymenella lasts but two or three days, 

 varying in different years from the last of April to the middle 

 of May, and almost every normal individual discharges its 

 sexual products at this time. The worms which are found 



