THE AXIAL GRADIENTS IN HYDROZOA. 



409 



tubes; for the same water is used in both tubes in each experi- 

 ment. The fourth column of figures gives the total volume of 

 the pieces in cubic millimeters, the fifth column the average 

 diameter of the pieces, and the sixth column the oxygen consumed 

 per cubic millimeter in the time occupied by the experiment. 

 Each experiment lasted four hours. In the first experiment six 



TABLE I. 



SHOWING THE CUBIC CENTIMETERS OF OXYGEN CONSUMED PER CUBIC MILLIMETER 



OF VOLUME IN FOUR HOURS BY APICAL AND BASAL PIECES 



OF THE STEM OF Tubularia. 



Duration of all experiments, four hours. 



pieces of stem were used; in the other experiments eight pieces. 

 The temperature was 20 C. in experiments I to 3 and 16 C. in 

 experiments 4 to 9. The volumes of oxygen as presented in the 

 table have been corrected for these temperatures. The nine 

 experiments are arranged in the table in the order of the diameters 

 of the stems used, largest first, smallest last. As already stated, 



