360 LIBBIE H. HYMAN. 



seasons of the year and were completely at variance with Banus's 

 statements. I was unable to verify any of his results. In 

 numerous experiments conducted for this purpose, the apical 

 halves of Tubularia stems regenerated markedly faster than the 

 basal halves of the same stems. I further believe that I dis- 

 covered the cause of Banus's peculiar results. My results are 

 presented in detail in the present paper. 



Not only are the researches just enumerated opposed to 

 Banus's statements but a large number of other facts concerning 

 the regeneration of Tubidaria clearly point to the existence of 

 axial differences in metabolic rate in this form. Thus all of the 

 facts collected by Driesch, Morgan, and Child concerning the 

 phenomena of "polarity" in Tubularia are entirely irreconcilable 

 with the view point of Banus and Loeb. If there is no axial 

 difference along the stem of Tubularia, why should the apical 

 end of a piece produce a hydranth and the basal end a stolon, 

 or if a hydranth, only later than the apical end? Why do 

 heteromorphic hydranths arise simultaneously on the two ends 

 of very short pieces while on long pieces the aboral hydranth is 

 delayed? This question has received no adequate answer except 

 that based on the axial gradient conception; in short pieces, 

 there is practically no gradient, and hence each end of the piece 

 begins to produce a hydranth at the same or nearly the same time; 

 while, in long pieces, the apical end by virtue of its higher meta- 

 bolic rate gets the start in hydranth formation and hence gains 

 control of the stem for a certain distance, thus inhibiting the 

 formation of the aboral hydranth. Why, as shown inde- 

 pendently by Driesch, Morgan, and Child, in an axial series of 

 very short pieces, do the apical pieces produce larger distal 

 structures with much reduced or absent proximal structures 

 while the more basal pieces give rise to smaller distal structures 

 and larger proximal parts? Longer pieces from the distal region 

 thus resemble shorter pieces from the proximal region in the 

 structures which they produce, owing to the pronounced tendency 

 of the distal pieces to use up their substance in the formation of 

 distal structures only. W'hy is the primordium of the oral 

 hydranth larger in apical than in basal pieces and the emerged 

 hydranth likewise larger? These and numerous similar facts 



