Cha?topterns Variopedatus. 525 



SPECIMEN NO. 2. SPECIMEN NO. 4. 



Distance Distance 



between arms. Date. between arms. Date. 



20 mm. Aug. T, 1905. 20 mm. Aug. 1, 1905. 



38 mm. Aug. 10, " 32 mm. Aug. 9, " 



60 mm. Aug. 15, " 61 mm. Aug. 16, " 



Early in September of 1905 I collected three worms whose tubes 

 averaged fifty-one millimeters between the orifices, and five wliose 

 recently discarded intermediate arms were sixty millimeters from 

 the ends with which they formed the small U-shaped tubes. The 

 horizontal extensions increased their lenglh to fifteen centimeters in 

 the smallest, and twenty-two and one-half in the longest specimen. 

 ]\Iany thick-walled tubes are found with scars of intermediate arms 

 which indicate that they were increased from about this size to forty 

 centimeters. The longest tubes show that they were increased, by a 

 linear extension of ten centimeters, to fifty centimeters. 



The tubes also undergo an enlargement in diameter as the animal 

 grows in thickness. This splitting and enlargement of one of its 

 arms I observed in specimen j^o. 4 during one night in September 

 of 1905. The worm pushed the rim of its buccal funnel nearly to 

 the margin of the orifice, and slowly moved the ends of the tentacles 

 over the rim of the tube. (In order to enter this narrow portion of 

 the tube from below the edges of the buccal funnel and anterior 

 region of the body were curved dorsalwards and considerably con- 

 tracted till they became conical in form.) The animal remained in 

 this position in the tube about five seconds, then slowly withdrew 

 into the deeper portion. This was repeated in thirty seconds, but 

 this time it withdrcAv only to the level of the sand. Here the worm 

 suddenly expanded the first pair of setigerous segments and split 

 the tube longitudinally at its outer side, then withdrew quickly into 

 the deeper portion of the tube. Fifteen or twenty seconds later the 

 worm reappeared at the level of the sand, extended the rent a little 



worm in No. 4 extended its tube to the glass wall of the aquarium on May 

 8-0. 19(j(;. The U-shaped tube now measured 85 millimeters between the 

 orifices. 



