4O2 LIBBIE H. HYMAN. 



time of regeneration of such apical and basal pieces is less than 

 is the case when pieces are cut from corresponding levels of 

 stems without branches. 



6. The difference in rate of regeneration of apical and basal 

 pieces of the stem of Tubularia can be reversed by putting both 

 sets of pieces for a certain time after cutting into appropriate 

 concentrations of depressing agents like cyanide and ether. 

 Under such circumstances the basal pieces regenerate in advance 

 of the apical ones on the whole. This is due to the fact that 

 depressing agents affect most strongly those regions having a 

 higher rate of chemical activity. Since apical pieces have a 

 higher metabolic rate than basal pieces, they are more affected 

 by the same concentration of depressing agent and hence their 

 regeneration is more retarded. In such cases the basal pieces 

 regenerate the more rapidly. That this explanation is correct 

 is further evidenced by the fact that the action of depressing 

 agents is greatly influenced by temperature. At lowered tem- 

 peratures a higher concentration of the agent must be employed 

 to obtain the same effect produced at higher temperatures by 

 lower concentrations. 



7. These results are in accord with those obtained by a number 

 of previous investigators and are directly opposed to the results 

 presented by Banus. Banus claims that there is no difference 

 on the average between the time of regeneration of oral hydranths 

 on apical and basal pieces of the stem of Tubularia. Personal 

 communication with Banus has elicited the fact that his usual 

 method of cutting the apical pieces was erroneous. He cut them 

 in such a way that the distal end of the apical piece was taken 

 just below the base of the hydranth. In such cases, as shown 

 in this paper, the distal ends of the apical pieces die away and 

 the regeneration and time of emergence of the oral hydranth 

 on these pieces is greatly delayed. It is believed that Banus's 

 results are invalidated by such a method of procedure. 



8. The results presented in this paper together with those of 

 others quoted in the paper show that the rate of regeneration of 

 pieces of Tubularia depends, when other factors are equal, upon 

 the level which those pieces occupied in the intact stem; it is 

 more rapid the nearer the pieces lie to the original distal end of 



