128 



Obsekyations on the Formation and Enlargement of the 



Tubes of the Marine Annelid, {Chaetopterus 



Variopedatus). 



HOWAKD E. Enders. 



Chaetopterus variopedatus is a widely distributed tubiculous auuelid 

 of tlie family Cliaeropterida. The individuals of each couutry aud of wide- 

 ly distributed areas iu Europe were classified as distinct species till Joy- 

 eux-Laft'uie showed conclusively, in 1890, that they are really a single 

 species. He also suggested that a close study of the species in foreign 

 seas would probably result in referring them to a single species. A care- 

 ful comparison of the specimens found at Beaufort, North Carolina, with 

 Joyeux-Laffuie's detailed description of Chaetopterus variopedatus, leads 

 me to regard the American representative, which Verrill and E. B. Wilson 

 named Chaetopterus peryanicntaceus, as identical with the single Eui'o- 

 pean form. 



This peculiar species of sedentary annelid is found in several localities 

 iu the harbor of Beaufort, North Carolina, where the conditions for its 

 existence are afforded by the extensive sand-flats, either covered with a 

 thick growth of diatoms or continually exposed to currents of water 

 heavily charged with these plants. It is here found living within its 

 broadly U-shaped parchment tubes in nearly every portion of the harbor 

 wherever' the sand-flats are formed in the quieter waters. 



The presence of Chaetopterus may be recognized by the extremities 

 of the U-shaped tubes that usually protrude several centimeters above the 

 level of the shoal (Fig. 3). The extremities of some tubes are concealed 

 by ascidians, colonies of bryozoans or of hydroids, attached to them so that 

 it may be ditRf-ult to detect the circular whitish openings within the cluster 

 of attached animals. 



The animal remains within its tube during its whole life but. as the 

 animal grows in size, it increases both the length aud the diameter of its 

 tube. The horizontal portion of the U is of greater diameter than the 

 conical vertical arms that protrude a few centimeters above the sub- 



