RELATIVE STABILITY OF LIVING MATTER 



Of the flat worms, the fresh-water planarians have remarkable 

 powers of regeneration. 



i. If the worm be cut in two at any point, each piece regen- 

 erates. If at or near the middle, two complete worms result, 

 though at first smaller than the normal. 



FIG. 37. Regeneration of head ends of Allolo- 

 boph or a fcetida 



A, B, too short for regeneration; C-E, longer anterior 

 pieces that made new segments; F (after Hazen), a 

 piece of five anterior segments grafted in a reversed - 

 position upon the anterior end of another worm (note a 

 heteromorphic head of two segments regenerated from 

 the free, which is the posterior, end). After Morgan 



2. If the cut be very near the head, the main por- 

 tion will of course regenerate perfectly, but the piece 

 removed will regenerate a reversed head, and the 

 anomaly results of a piece with a head on either end but no body 

 (see Fig. 38, F). 



3. If a piece be removed from the middle by transverse ( 

 each part regenerates and three worms result. 



