332 



L. H. HYMAN AND A. W. BELLAMY. 



paring the apical and basal ends of branches or terminal portions 

 of the main axis ; the apical end is negative to the basal end and 

 the p.d. is greater along the distal part of the main axis than along 

 the proximal part, and greater along the distal part of the main 

 axis than along lateral branches. Thus No. 3 in Table III. gives 



TABLE III. 



ELECTRIC GRADIENT OF Pennaria tiarella AND Obelia borealis. 

 Symbols as in Table II. 



the potential difference between the terminal hydranth and the 

 stem proximal to it ; Nos. 4 and 5 give the difference along lateral 

 branches of the same colony. No. 6 is the main axis of a colony; 

 Xos. 7 and 8 lateral branches of the same colony. Nos. 9, 10, and 

 ii give the potential differences along a distal lo-mm. piece, middle 

 lo-mm. piece, and a basal lo-mm. piece, respectively, of a colony. 

 No. 14 gives the potential difference between the apical and basal 

 regions of a large colony; Nos. 17 and 18 of distal branches of 



