560 



S. M or gill IS 



ably different in size should have different regenerative capacities; 

 still these differences are of little account when we take into con- 

 sideration the regenerative capacity of pie;es intermediate in size. 

 Thus a piece of only fourteen segments belonging to the same level 

 of the worms regenerated sixty-six segments, or six segments more 

 than the piece of twenty-nine segments. 



In view of this evidence we may safely assume that the length of 

 a piece has no direct relation to the rate of its regeneration, and 

 that the rate is dependent upon the position of a piece in relation 

 to the worm's head. The pieces nearer to the head have the 

 highest regenerative power, which gradually decreases as we pass 

 from the front backward. 



I wish also to point out in this connection the great range of 

 variability in the regenerative power of various worms, that can be 

 easily seen on looking over every column of the table. 



Al Az A3 A4 As Ae 



Diagram showing the rate of regeneration at different levels. 



In the accompanying diagram an attempt is made to demon- 

 strate the rate of regeneration at different levels by means of rec- 

 tangles. The horizontal lines represent the "ideal" old segments 

 of different levels, whereas the vertical ones represent the "ideal" 

 number of new segments, regenerated at these levels. In either 

 case a segment is expressed by a line i cm. long. 



The worms were kept in clear, filtered water, so that they did 

 not have any food for two weeks, but since the pieces had no heads 

 they would not have been able in any case to feed for a greater 

 part of the time. 



After fourteen days (November 21) the pieces A^ to Ag were 

 examined again. It will be remembered that on November 8, 



