no INDIVIDUALITY IN ORGANISMS 



to a head, and vice versa, and it also means that the 

 higher the metabolic rate in the region y^ the less likely 

 the piece is to give rise to a head. If this relation is 

 altered by an increase of rate % relatively to rate y^ head- 

 frequency is increased; if by an increase in rate y rela- 

 tively to rate x^ head-frequency is decreased. On this 

 basis all the experimental effects of different physio- 

 logical and external conditions on head-formation can 

 be readily accounted for, and it has even been possible 

 in many cases to predict the results of various experi- 

 ments. 



Some of the facts on which this conclusion is based 

 are as follows: By means of the susceptibility method I 

 have demonstrated that the act of section always in- 

 creases metabolic rate, particularly in the part basal 

 to the cut. This condition of stimulation continues in 

 the pieces for several hours after cutting and only gradu- 

 ally disappears.^ The more basal the level of the piece 

 in the original body, the more its metabolic rate is 

 increased by section. In the cases of pieces a, ft, c in 

 Fig. 57 the metaboHc rate during the first few hours 

 after section is higher in h than in a and higher in c than 

 in h, although before section the rate decreased from 

 a to c. This difference in stimulation of pieces from 

 different levels results from the different degrees of 

 subordination. The region c is subordinate to all more 

 apical regions and is much more dependent upon 

 impulses coming from these regions than is the region a, 

 which is subordinate only to the head. When the chief 

 paths of conduction in the nervous system are cut they 



^ Child, "Studies on the Dynamics of Morphogenesis. VII," 

 Jour, of Exp. Zo'ol., XVI, 1914. 



