Vol. XXXVIII. June, 1920. No. 6 



BIOLOGICAL BULLETIN 



THE AXIAL GRADIENTS IN HYDROZOA. III. EX- 

 PERIMENTS ON THE GRADIENT 

 OF TUBULARIA. 



LIBBIE H. HYMAN, 

 HULL ZOOLOGICAL LABORATORY, UNIVERSITY OF CHICAGO. 



A. INTRODUCTION. 



In a recent paper Banus ('18) states that there is no difference 

 between the time of regeneration of oral hydranths on apical and 

 basal pieces of the stem of Tnbularia. The data presented by 

 Banus apparently support this conclusion. Such data are, how- 

 ever, of no significance unless complete information is given as 

 to the manner in which they are obtained. Perusal of Banus's 

 paper reveals the fact that absolutely no information is imparted 

 concerning the conditions under which the experiments were 

 performed or the manner of handling the material. Those who 

 have worked on the physiology of the lower forms are well aware 

 that experimental results can be readily controlled and modified 

 by conditions. It is, therefore, impossible for the impartial 

 mind to accept the validity of Banus's conclusions, until further 

 information concerning his experiments shall be forthcoming. 

 Grave doubt is cast upon the correctness of Banus's statements 

 by the fact, completely ignored by him, that experiments of this 

 kind had already been performed several times, with results 

 contrary to his. In addition to these omissions, Banus has 

 made a number of exaggerated and misleading statements. 



Banus begins by saying that Child "assumes the existence of 

 metabolic gradients in a great number of species of animals and 

 plants and on this assumption he builds a theory of individual- 

 ity." In view of the great mass of data which has been presented 

 concerning metabolic gradients and the extent to which these 



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