Rate of Regeneration. 367 



or the regenerating buds of the chelae and walking legs receive less 

 food material than do the same organs when uninjured. As the 

 total amount of food material to be distributed is by hypothesis 

 constant it follows that when a greater number of appendages 

 is removed the surplus of material is greater. The surplus of 

 material is therefore greater in Series B than in Series A and 

 crowds upon both the regenerating parts more vigorously than in 

 the latter. The regenerating buds in Series B, the series with the 

 greater injury therefore grow more rapidly than those of Series A. 

 Evidently when the degree of injury becomes great enough to dis- 

 turb the mechanism of production of food material so that the 

 amount of the latter is diminished and there is no longer a con- 

 stant quantity K, the present statement cannot hold. 



4. The results of the experiments on the relation between the 

 degree of injury and the rate of regeneration of the crayfish and 

 the brittle-star bring out very strongly an essential difference 

 between crystals and organisms. In the former no matter what 

 the number of removed parts the growth of each in a nutrient solu- 

 tion is entirely independent of the number or character of other 

 removed parts in the same crystal. In the organism on the other 

 hand there is no such independence. No part of the organism can 

 be removed without affecting all other parts. This difference 

 may, however, be due to the difference in the nature of the food- 

 supply and not to an essential difference in the structures them- 

 selves. In crystals the food material is external and practically 

 inexhaustible. Each part is thus independent of restrictions due 

 to amount of food material. 



5. The stimulation ot the nerve of a leg or arm as a result of 

 the injury to that member may be supposed to induce the processes 

 leading to its regeneration. If it is assumed that an increase in 

 stmiulation causes more than a corresponding increase in intensity 

 of such processes there will result a greater rate of regeneration in 

 an animal with a greater injury than in one with a lesser injury. 

 Physiologists have found that in general the curves tor increasing 

 stimulus and increasing response are not parallel. In some cases 

 and this is especially true near the lower limits of the curves, the 

 response curve runs up faster than does the stimulation curve. 

 The organism possesses some inertia in every case and it is neces- 

 sary to overcome this before any response at all is obtained. Hav- 

 ing passed the lower limit, however, there is a very rapid upward 



