METABOLIC GRADIENT IN ANNELIDS 7 



consume the most oxygen, pieces from the anterior end less oxy- 

 gen, and pieces cut slightly anterior to the middle the least 

 oxygen. This was found to be the case. 



2. The electrical evidence. To complete the evidence brief 

 mention may be made of the electrical gradient and galvanotaxis 

 of oligochaetes. It has been found that the anterior and posterior 

 ends of oligochaetes are electronegative (galvanometrically) 



Fig. 1 Graph of the death gradients in cyanide of three individuals of Lumb- 

 riculus inconstans. Segments on the abscissa; time of death in hours on the 

 ordinate, reckoned from the beginning of death, not from time in the killing solu- 

 tion. Heads of animals to left; posterior ends to right. The high peak near the 

 posterior ends of two of the individuals is due to the presence of a zone of 

 autotomy. 



to the middle, and further that when placed in an electric current 

 the worms bend into a general U-shape, with anterior and 

 posterior ends directed toward the cathode and middle region 

 directed toward the anode.^ These facts further indicate that 

 the anterior and posterior ends of oligochaetes have a higher 

 metabolic rate than the middle regions, ' 



3 Cf. further Hyman ('18). Near the top of the second column on page 523 

 in this paper the statement that oligochaetes in a current 'travel to the anode' 

 should read 'travel to the cathode.' 



