124 LIBBIE H. HYMAN 



III. THE DATA OF REGENERATION 



1 . The head region of oligochaetes 



I have frequently used the term head region or head in speak- 

 ing of these organisms and I wish now to explain what is meant 

 by this expression. The head of oligochaetes comprises a 



Fig. 18 Four stages in the disintegration of Tubifex rivulorum at hatching. 



definite number of the most anterior segments, which are gener- 

 ally sharply marked off from the rest of the body; the exact 

 number of segments involved varies with the species. The chief 

 distinguishing characteristic of the head is that it contains the 



