498 Howard Echviii Enders, 



periphery of the tube or to protrude slightly from a lateral rent 

 which is formed during the enlargement of the tube, it is rarely 

 seen protruding beyond the orifice. N^evertheless, during a rising 

 tide after an unusually long exposure of the shoals near mid-day 

 one worm protruded the whole anterior region beyond the orifice 

 and again withdrew into the interior. This seems to have repre- 

 sented an effort to avoid the warm water which remained in the 

 tube. A single adult specimen which I collected during the same 

 season had begun to regenerate the portion before the fourth setiger- 

 ous segment, the one which bears club-shaped black setse. A new 

 mouth had formed, but it lacked the characteristic thick lips which 

 form quite early in the larva of Chcetopterus. Probably the pro- 

 truded portions of the worm were bitten off by some passing fish. 

 When these annelids are removed from their tube they may be kept 

 several days in well aerated water without any sign of forming a 

 new^ tube or any portion of a tube. After they were exposed two 

 days outside of their tubes they began to macerate and soon died 

 even if kept in well aerated w^ater, but several specimens wdiich were 

 transferred to the broadly U-shaped glass tubes in an aquarium of 

 running sea water were kept alive nearly three weeks. 



I have reason to believe that the individuals which are kept in 

 the glass tubes continue their normal bodily movements and behave, 

 in general, as they would in their own parchment tubes. The glass 

 U-tubes therefore serve as convenient receptacles for making con- 

 tinuous observations on their habits. 



When Chsetopterus is placed in a broad U-shaped glass tube about 

 the same size as the parchment tube in which the animal was found, 

 it takes a position in its horizontal portion. Here it lies on its ven- 

 tral side with the adhesive discs of the twelfth, thirteenth and four- 

 teenth segments attached to the Avail of the tube. The notopodia 

 sway back and forth in the water while the neuropodia are in con- 

 stant rhythmic motion backwards. The distal ends of the notopodia 

 of the twelfth segment are usually joined over the dorsal side, and 

 the thirteenth segment is contracted so that the accessory feeding- 

 organ which it bears is tilted forwards (Figs. 8, 4) till it lies within 

 or immediatelv back of the arch formed by the union of the noto- 



