496 THE AMEBIC AN NATURALIST [Vol. XLIX 



segments were removed; and in the sixth eight posterior 

 segments. The worms were anesthetized with chloretone, 

 and the operation was performed under a dissecting mi- 

 croscope. The pieces were placed in small sterilized glass 

 bottles, each containing a strip of filter paper and enough 

 sterilized sea water to keep the animals well moistened. * 

 Ten pieces of approximately the same length were kept 

 in a single bottle. Throughout the experiment the bot- 

 tles, each one stoppered with a cork, were kept in an ice 

 chest to restrict the growth of bacteria. The work was 

 begun early in July, 1913, and was continued until the 

 first of October. At the middle of August it became nec- 

 essary to carry away from the seashore the material then 

 living. After this, fresh water was used for moistening 

 the worms and cleaning out the bottles. The worms, 

 however, seemed to regenerate as well in the fresh-water 

 as in the salt-water environment. The analysis of the 

 results of the experiments was done in the zoological labo- 

 ratory of Harvard University. 



It was found that the length of the regenerated seg- 

 ments, as compared with that of the segments in the adja- 

 cent unregenerated part of the worm, was a fairly accu- 

 rate criterion for determining the number of regenerated 

 segments. To test the accuracy of this criterion, parts 

 of eight worms consisting of the twenty most anterior 

 segments were allowed to regenerate for about eight 

 weeks. Having taken the precaution to determine accu- 

 rately the number of segments in each of the pieces at the 

 time of the operation, it was easy to determine how many 

 segments had regenerated, for of the total number of seg- 

 ments at the end of the experiment all except the original 

 twenty were, of course, regenerated segments. The re- 

 sult thus obtained was compared in each worm with that 

 obtained by counting in the same worm the number of 

 segments posterior to the point where there was an abrupt 

 change in the length of the segments, that point indicat- 

 ing the region of the cut. Table I gives the data for this 

 comparison. The results show that the method which 



