PROCESS OF REGENERATION 



139 



This table shows that the different kinds of anterior structures 

 are not very sharply localized along the axis, but that in general, 

 the percentage of inhibited forms is greater in posterior regions. 

 The increase in percentage of normal heads in extreme posterior 

 pieces (fourteenth and fifteenth pieces in the table) appears to 

 be a general result, and is probably due to two factors: first, 

 owing to the decrease in size of segments posteriorly, these pieces 



TABLE 1 

 2 3 4 5 6 7 8 9 10 11 12 13 14 15 



Normal 



Hypoprostomic 



Aprostomic 



Acephalic 



Cephaluran outgrowths 



Biaxial tails 



Multiple outgrowths — 

 Dead 



9 segments 



8 



7 *. 



6 



5 



4 



3 



TABLE 2 



contain more segments than anterior pieces of equal length, and, 

 secondly, these pieces are in the region where autotomy occurs,^ 

 and where, therefore, new individuals already exist to some extent 

 physiologically. Similarly, in Planaria dorotocephala (Child, 

 '11 b), pieces from the levels where the zooids are situated gener- 

 ally produce normal wholes. 



In table 2, the number of head segments regenerated by the 

 same sixteenth pieces is given (cephaluran outgrowths and biaxial 



* Lumbriculus inconstans reproduces asexually by autotomy. Upon stimu- 

 lation, this worm breaks in two at a rather definite level, near the posterior end of 

 the body. 



THE JOURNAL Or EXPERIMKNTAI. ZOOr.OGT, VOL. 20, NO. 2 



