50< i 



THE AMERICAN NATURALIST [Vol. XLIX 



The worms seemed to regenerate equally well in a fresh- 

 water or in a salt-water environment. Thirty-one of the 

 one hundred and sixty surviving worms lived for about 

 forty days in a fresh-water environment and regenerated. 

 Twenty-six worms from which the sixteen posterior seg- 



ments had been removed, and twenty-six others from 

 which the posterior half had been removed, regenerated 

 almost contemporaneously for about thirty days in the 

 same ice chest, and in a salt-water environment. Later 

 in the season in a different ice chest eighteen worms from 

 which the sixteen posterior segments had been removed, 

 and thirteen from which the posterior halves had been re- 

 moved, regenerated contemporaneously for about forty 

 days in a fresh-water environment. "When the sixteen 

 posterior segments were removed the rate of regeneration 



less than in the fresh-water environment, while when the 

 posterior halves were removed the rate of regeneration 

 in the salt-water was 0.07 segments per day greater than in 



