Soiuo Phononu-na uf Rcgcnt-iation in Limiiodrilua aiid related Forms. 397 



the posterior eiid capable of regeiierating. In Lumbriculits, Table I, 

 the posterior 20 somites did not live and the 20 somites immediately 

 anterior to the posterior 20 did not regenerate and but one piece at 

 this level lived while of the pieces at the third level from the poste- 

 rior end 50 per cent lived and regenerated. Of the pieces 15 somites 

 long, Table II, the last and the next to the last posterior set did not 

 live while 50 per cent of the third to the last set regenerated. To de- 

 termine niore closely the size of a piece near the posterior end in Lum- 

 hriculm capable of living and regenerating some further experiments 

 were made. 



July 21st 1908. The posterior thirty somites were cut from 

 20 Worms. A week later all these pieces were dead. 



July 22nd 1908. The posterior ten somites were taken from 

 20 Worms and then the twenty-five somites next anterior to these weie 

 cut off. At the end of a week one piece twenty-five somites long had 

 regenerated six somites at the anterior end and six at the posterior 

 end. The other pieces died, 



July 24th 1908. The posterior thirty -five somites were cut from 

 20 Worms. A week later three of these pieces had regenerated six or 

 seven somites at the anterior end. 



Thus it is Seen that in Lumbriculus the minimal size of a piece 

 from the posterior end capable of regenerating is thirty-five somites 

 while ten somites from the posterior end pieces of twenty-five somites 

 can regenerate at both the anterior and the posterior end. 



On the other hand in Limnodrilus the level at which 

 fifteen somites can live and regenerate at the posterior end is still 

 farther anterior. Table III shows that at the four posterior levels a 

 piece of this size does not Hve w'hile but two pieces at the 5th level from 

 the posterior end regenerated. For pieces twelve somites long the 

 results are much the same. 



The Intestine and Eegeneration. 

 A. Posterior End. 

 On looking over some specimens of Limnodrilus from which the 

 greater part of the posterior end of the body had been cut off niy atten- 

 tion was attracted by a peculiar coiidition of affairs which existed in 

 one of them. The intestine terminated a short distance from the 

 end of the body and its posterior end was free, not being connected 

 with anything, furthermore it had not regenerated. Neither had the 

 body wall regenerated nor formed an anal opening. The worm had 



