CORRELATION BETWEEN METABOLIC GRADIENTS. 



331 



corded in Table 2 were made upon branches of the colonies ; the 

 apical regions of such branches are negative (galv.) to the basal 



TABLE II. 



ELECTRIC GRADIENT OF Obelia geniculata, Schizotricha tcnella, AND Euden- 



drium ramosum. 



Negative and positive refer to direction through the galvanometer. Read- 

 ings are divisions of the scale of the galvanometer. Ap., apical ; bs, basal ; 

 rd., galvanometer readings. 



levels. In Nos. 3, 10, 15, and 21 a short piece was removed from 

 the apical end of the main axis of the colony, and the potential 

 difference between the apical and basal ends of this piece tested; 

 the former is again negative (galv.) to the latter. In Nos. 24 

 and 25 the terminal zooid of the colony was compared with one of 

 the lateral zooids, the two being connected by a strip of filter 

 paper soaked in sea-water; the former is negative (galv.) to the 

 latter, as was found also in Obelia borealis. 



Pennaria tiarclla. This species forms large, open, branching- 

 colonies. Most of the data in the table were obtained by com- 



