176 ADA R. HALL 
2. Differentiation of this plug material takes place. The 
nuclei elongate and orient themselves in the direction of the 
muscle pull. Definite fibers with a dark-staiming reaction are 
formed here also. In the region of the nerve strand the nuclei 
are fewer and the fibrillar material has a different staining 
reaction—one which is similar to that of the fibrillar portion of 
the original cord. This may occur as early as fourteen days 
and is present before recovery of movements takes place, indicat- 
ing the actual presence of nerve fibers before functioning can 
take place. 
3. Complete recovery takes place, with ganglion cells formed 
in'each metamere of the completed cord and with the coelom 
entirely free from extra cell structures. 
GENERAL CONCLUSIONS 
1. There is a rapid formation of cicatrix material which closes 
the wound. This comes from the cells in the blood, a tissue 
easily brought in to fill the gap. 
2. There is a definite growth of nerve fibers from the ends of 
the cord into the strand formed by the cicatrix material. Large 
ganglion cells may also migrate into the strand if the cut is 
through a ganglion, thus restoring the tissue to its normal 
condition. 
3. If several ganglia are removed, a strand is formed as in 
simple regeneration to fill the gap, and fibers and ganglion cells 
are replaced by outgrowth from the cut ends. If a long period— 
two to three months—is allowed for further growth after the 
normal movements return, all extra cells are absorbed, so that 
the worm appears perfectly normal in every respect. 
DISCUSSION OF RESULTS 
This growth and regeneration of the annelid nerve cord seem 
at first glance remarkable for the speed of recovery. The cord 
is cut and in from four to six days the normal movements and 
impulses are again present in the worm. From a study of the 
process we may conclude that the central nervous system has 
