358 G. E. GATES. 



tion three individuals had regenerated hypomeric anterior ends, 

 one had produced a hypermeric anterior end and the others had 

 exactly replaced the number of segments lost. The single worm 

 with hypermeric regeneration had lost the first thirteen segments 

 as well as dorsal portions of segments xiv and xv and had not only 

 replaced the lost dorsal portions but had also formed fifteen per- 

 fectly normal and clearly outlined setigerous segments and the 

 non-setigerous prostomial segment. 



TABLE IV. 

 COLLECTION NUMBER i. 



Normal worms 231 



Mutilated worms 104 



Worms with tail mutilation 98 



Worms with head mutilation 6 



Worms regenerating a tail 77 



Worms regenerating a head 3 



COLLECTION NUMBER 2. 



Normal worms : 301 



Mutilated worms 87 



Worms with tail mutilation 84 



Worms with head mutilation 3 



Worms regenerating a tail 71 



Worms regenerating a head 2 



COLLECTION NUMBER 3. 



Normal worms I 



Mutilated worms 6 



Worms with tail mutilation 5 



Worms with head mutilation I 



Worms regenerating a tail 3 



Worms regenerating a head i 



COLLECTION NUMBER 4. 



Normal worms ? 



Mutilated worms ? 



Worms regenerating a tail 49 



Worms regenerating a head 4 



It is evident therefore that both in its natural environment and 

 tinder experimental conditions in the laboratory P. excavatus may 

 regenerate hypermeric anterior ends. In view of this demonstra- 

 tion there seems to be no need for further search, at least for the 

 present, for other explanation of the origin of the anomalous 



