374 LIBBIE H. HYMAN. 



I therefore find, as Mathews did, that within the limits of a 

 single Tubularia individual, any distal region is electronegative 

 (galvanometrically) to any proximal region. Since electro- 

 negativity is usually associated with a higher rate of oxidative 

 metabolism in organisms, these experimental data constitute 

 strong evidence that there is a metabolic gradient along the 

 axis of Tubularia, that the apical end of this axis has the highest 

 rate of activity, and that this rate diminishes proximally. 



E. DIFFERENCES IN RATE OF REGENERATION OF DISTAL AND 

 PROXIMAL PIECES OF EQUAL LENGTH. 



A large number of experiments were performed with reference 

 to this point with the result that the apical pieces were found 

 to regenerate markedly faster than the basal pieces in practically 

 all cases. A few cases were observed in which the proximal piece 

 regenerated first. 



i. Method of Procedure. The method of cutting the pieces 

 was invariably as follows unless specifically stated otherwise. 

 Stems free from branches and filled with coenosarc throughout 

 their length were removed from the colony and placed on a glass 

 plate. The hydranth and the first millimeter or two of the stem 

 were then removed by a cut and discarded and the basal end 

 injured by removal from the colony also cut off and discarded. 

 The piece of stem was then cut into two equal halves, a distal or 

 apical half and a proximal or basal half. In most cases, unless 

 otherwise stated, such halves were 8-12 mm. long. Figure I 

 illustrates the method of cutting the pieces. 



After cutting the pieces were handled in two different ways. 

 In the majority of the experiments all of the apical halves were 

 placed in one finger bowl and all of the basal halves in another 

 finger bowl. Such experiments are designated throughout this 

 paper as mass experiments. The number of oral hydranths 

 emerged in each finger bowl at a given time was then recorded. 

 In other experiments, which are designated as individual experi- 

 ments, each half was placed in a separate stender dish and the 

 time of emergence of the oral hydranth on each half stem recorded 

 as accurately as possible. In all cases the record was taken only 

 when the hydranth had emerged completely from the perisarc. 



