Studies on Regulation. 535 



the others presented in the eadier sections and show that the degree 

 of contraction of the cut surface is not the determining factor as 

 regards the amount of regeneration, but that both the contraction 

 and the regeneration are determined by other factors certain of 

 which differ quaHtatively according to the level. 



6. Resume of the Experiments 0/7 Anterior Regeneration. 



The preceding sections have estabHshed several facts of impor- 

 tance regarding anterior regeneration. It has been found that 

 at all levels anterior to the middle of the cephalic ganglia anterior 

 regeneration is complete and its rapidity is in general proportional 

 to the size of the part removed. At all levels posterior to the 

 middle of the cephalic ganglia anterior regeneration is incom- 

 plete and the rapidity and amount of regeneration are in general 

 inversely proportional to the size of the part removed, /. e., the 

 further posterior the level from which regeneration occurs the 

 less the rapidity and amount of regeneration. Complete regen- 

 eration of the cephalic ganglia is possible when no more than half 

 the ganglionic material is removed, but never occurs after the 

 removal of a larger part or all of the ganglionic material. When 

 the ganglia are absent, or if they fail to regenerate completely, 

 nothing that can properly be called a head is regenerated. A close 

 parallelism between the degree of motor activity and the power 

 of regeneration exists in all cases. The relation between the 

 cephalic ganglia and anterior regeneration is very different from 

 that between the ganglia and posterior regeneration (Child, '04b). 

 Posterior regeneration is qualitatively complete, though some- 

 what reduced in amount in the absence of the ganglia while under 

 similar conditions anterior regeneration is both qualitatively and 

 quantitatively incomplete in high degree. The correlation be- 

 tween the ganglia and posterior regeneration, which is merely 

 quantitative, was interpreted in the preceding paper as essentially 

 functional, the motor activity of the parts being much greater 

 though not widely different qualitatively when the ganglia are 

 present. As regards anterior regeneration the case is different; 

 the motor activity of this region of the body is not only less in 

 degree in the absence of the ganglia but it is different in kind. 



