Regejieration in Lnriihri cuius 557 



Experiment I (October 14). A number of pieces were cut off 

 and allowed to heal for about eighteen hours. Then still smaller 

 pieces were cut off near the closed ends. 



a From the anterior half of the worms I obtained: two pieces 

 of five segments each; five pieces of four; eight pieces of three; six 

 pieces of two; and two pieces of one segment each. 



Most of these pieces were found dead about the second day after 

 the operation. On October 19, the survived pieces, containing 

 5, 4, 4, 4, 3, 2, 2 old segments, had all regenerated a head and a tail. 



b From the posterior halves of the same worms, I obtained: 

 five pieces of five segments each; eight pieces of four; nine pieces 

 of three; two pieces of tw^o; and two pieces of one segment each. 



October 19, the surviving pieces of 5, 5, 5, 4, 4, 4, 4, 3, 3, 3, 3, 

 2, 2 had all regenerated a head and a tail. 



This experiment shows that pieces containing only two segments 

 are capable of regenerating. 



Experiment II. a By following the same method, pieces from 

 the anterior half of the worms, consisting of 3, 3, 3, 3, 2, 2, 2, i, i, 

 I old segments also produced a new head and tail. 



This experiment showed very distinctly that a single segment 

 is capable of maintaining its existence, and of regenerating a 

 perfect head, consisting, as is usually the case, of six segments, 

 and also a tail. 



h From the posterior halves of the same worms, I got thirteen 

 pieces of three segments each; sixteen of two segments and twelve 

 of one segment. Of these there regenerated eight pieces of three 

 segments, seven pieces of two segments each, and none consisting 

 of one segment only. 



B Rate of Posterior Regeneration 



The object of the following experiments was to determine 

 whether the length of the piece or its relative position in the worm's 

 body is directly responsible for the rate of its posterior regenera- 

 tion. - 



Experiment III (October 25). About thirty-five worms were 

 divided into seven parts each. The seventh piece (the tip of the 



8 Archiv. f. Entwickelungsm., xiv, p. 586, 1902. 



