590 LIBBIE H. HYMAN. 



they are near the apical ends of new individuals (the real apical 

 end being the hydranth of the branch) will have a higher meta- 

 bolic rate than ordinary basal pieces. Owing to the operation of 

 both of these factors it may be expected that the difference 

 between apical and basal pieces will be reduced when they are 

 cut above and below, respectively, the level of a branch. This 

 was found to be the case. Banus in his paper does not state 

 whether or not he used stems free from branches and did not 

 reply to inquiries on this point. 



In preparing pieces for this kind of experiment, the following 

 procedure was usually adopted. Stems having one branch at 

 about the middle of the stem were selected, the terminal hy- 

 dranth, upper millimeter or two, and basal end cut off and dis- 

 carded as usual. An apical piece was then cut anterior to the 

 branch, and a basal piece of equal length posterior to the branch; 

 the small piece bearing the branch was discarded. As found by 

 Morgan and verified in my experiments, the stumps of lateral 

 branches left on pieces w T ill regenerate hydranths more rapidly 

 than the distal end of such pieces, and these lateral hydranths 

 will then inhibit the formation of the terminal hydranth; hence 

 in experiments of this kind it is necessary to avoid using pieces 

 bearing stumps of branches. The method of cutting the pieces 

 in most of the experiments is illustrated in Fig. 3. In one 

 experiment, stems having two branches were selected, the apical 

 piece cut in front of the first branch, and the basal piece between 

 the two branches as illustrated in Fig. 4. 



The results are presented in Table VIII. All experiments of 

 this kind were mass experiments. Experiments I2a and 126 

 were performed in June at room temperature, the remaining 

 experiments in December at 12 C. 2. The controls for these 

 experiments are indicated at the top of the table; such controls 

 were cut at the same time and from the same lot of material, 

 with the exception that they came from stems without branches, 

 and were kept under the same conditions. The pieces in experi- 

 ments 28, 30, and 34 were short pieces, 5-10 mm. long; those in 

 experiments 12 and 36, approximately 10 mm. long. The pieces 

 for all experiments except number 36 were prepared according 

 to Fig. 3; those for experiment 36 as in Fig. 4. 



