102 Papers from the Marine Biological Laboratory at Tortugas. 



SUMMARY. 



The marine annelid worm Amphinoma pacifica readily regenerated a 

 head at all levels except the distal eighth of the worm. 



The formation of a tail occurs only in the posterior half or third of the 

 body. 



Only in the median levels of the body can the two cut surfaces regenerate 

 a head and a tail respectively. 



Regeneration may be prevented by a severe injury, either to the digestive 

 tract or to the central nerve system; the greater the injury the more likely 

 will regeneration be inhibited. 



Many pieces did not regenerate after removing the alimentary tract 

 from five or more segments nearest the amputated level. 



Many pieces, about one-third, failed to regenerate after removing the 

 nerve-cord by the forceps, i. e., with little injury to adjoining tissues. 



All failed to regenerate after removing the nerve-cord by the "window" 

 method, i. e., with serious injuries to adjoining parts. 



The operated worms were examined in serial sections. In one group a 

 regenerated nerve-cord connected the regenerated "brain" and commissures 

 with the old intact nerve-cord. 



In a second group the regenerated nerve-cord approached and in many 

 instances reached the amputated level, yet no head was formed. 



In a third group, the nerve-cord had regenerated, but several segments 

 nearest the amputated end were yet without any nerve-cord or ganglia. 

 These worms nevertheless had regenerated a head with its typical brain and 

 nerve-commissures. 



The last group completes the demonstration that Amphinoma as well as 

 Lumbricus can regenerate without the contact of, or stimulation from, the 

 nerve-cord or central nervous system. 



