148 



LIBBIE H. HYMAN 



other parts; posterior regions are, on the other hand, dependent 

 on anterior parts and subordinate to them, since thp severance 

 of conduction paths between them results in stimulation. 



The increase of metabolism after section is only temporary. 

 If the pieces are tested in cyanide at various intervals after cut- 

 ting, it is found that the susceptibility to cyanide gradually 

 decreases to far below normal, and then begins to rise again 

 as regeneration sets in. For an analysis of the process of head 

 formation, it is necessary to know what the metabolic condition 



TABLE 5 

 Susceptibility <jj' slxirt (intirlor piece de to KCN g-^Q^a^ various tixies after cat tin (^ 



of the pieces is during the period in which the head is determined. 

 I have therefore tested the susceptibility to cyanide of short 

 anterior and posterior pieces of Lumbriculus. In table 5 is 

 given the susceptibility to cyanide of the anterior piece de in 

 figure 23, immediately, 5, 17, 24, 48, and 96 hours after section; 

 and in table 6, the susceptibility of the posterior piece ah in figure 

 23 immediately, 5, 14, 19, 24, 48, and 96 hours after cutting. 

 Ten pieces are used in each case, and the time of death of cor- 

 responding regions of whole worms also noted. The concen- 

 tration of cyanide used was.^^-o; observations were taken every 



