THE AXIAL GRADIENTS IN HYDROZOA. 



399 



the number of pieces having aboral hydranths. In experiment 

 49, six such pieces had failed to give rise to oral hydranths when 

 the experiment was concluded and in three of these cases, no 

 primordia of the oral hydranths were present, the polarity having 

 been completely reversed. 



The data given in Table XI. show in a very striking manner 

 that the regeneration of apical pieces cut so that their distal ends 



TABLE XI. 



RECORD OF MASS EXPERIMENTS ON THE RATE OF REGENERATION OF APICAL 

 AND BASAL PIECES OF EQUAL LENGTH WHEN THE DISTAL END OF THE APICAL 

 PIECES is TAKEN AT THE BASE OF THE ORIGINAL HYDRANTHS. 



are just at the base of the original hydranths is markedly delayed 

 and that in the majority of cases, the basal pieces regenerate first. 

 It should be remarked that the delay is chiefly in the time of 

 emergence of the oral hydranths and not in its formation; for 

 the primordia of the hydranths in these apical pieces form in 

 advance as a rule of those of the corresponding basal pieces; 

 but these hydranths can not emerge as rapidly owing to the 

 fact that they must be pushed through the piece of empty 

 crumpled perisarc left by the death of stalk region. 



The data in Table XI. furnish the explanation of Banus's 

 results. It is obvious that anyone who practices the method of 

 cutting the apical pieces described in connection with this table 

 and who mixes up such a method with procedures where "more 



