REGENERATION POSTERIORLY IN ENCHY- 

 TR^EUS ALBIDUS 1 



H. R. HUNT 



The primary object of the following experiments was 

 to determine whether Enchjitraus alhidits can regenerate 

 posteriorly, when cut at regions of the body varying from 

 near the posterior end to near the anterior end. Sec- 

 ondly, an attempt was made to compare the rates of re- 

 generation per day posteriorly at the different levels at 

 which the worms were cut in two. 



No experiments have been published in which the ca- 

 pacity of this species to regenerate posteriorly has been 

 tested. Nusbaum ('02; '04) studied the histological 

 processes in the regeneration of the Enchytraudse ante- 

 riorly and posteriorly. He found that regeneration ante- 

 riorly does not take place as readily as regeneration pos- 

 teriorly, and that never more than two or three segments 

 regenerate anteriorly. 



The animals used in the present experiments were col- 

 lected in abundance from the coarse gravel of the tidal 

 zone on the seashore at Cold Spring Harbor, Long Island, 

 New York. Six sets of experiments were conducted. 

 Each of the worms was cut into two pieces, the anterior 

 and the posterior pieces being preserved. The average 

 number of segments in this species is not far from sixty. 

 The regions selected for cutting were such as to give 

 fairly comprehensive data as to the regenerative capacity 

 posteriorly at different levels. In the first set of experi- 

 ments the worms were so cut as to leave only about eight 

 anterior segments ; in the second set about sixteen anterior 

 segments ; and in the third set about twenty anterior seg- 

 ments. In the fourth set the cut was made near the 

 middle of the worm; in the fifth about sixteen posterior 



1 Contributions from the Zoological Laboratory of the Museum of Com- 

 parative Zoology at Harvard College, No. 260. 



495 



