AN EXAMINATION OF THE PROBLEMS OF PHYSIO- 

 LOGICAL "POLARITY" AND OF ELECTRICAL 

 POLARITY IN THE EARTHWORM. 



T. H. MORGAN AND ABIGAIL C. DIMON. 



The so-called "polarity" exhibited in the regeneration of ani- 

 mals has suggested the idea to a number of writers that the phe- 

 nomenon might be related to, or the outcome of differences in 

 potential in different regions; or, in other words, of electrical polar- 

 ity. The term "polarity" itself, which has been generally adopted 

 to express a sort of stereometric relation in the regeneration of 

 living things, suggests in certain striking ways the polar relations 

 observable in many electrical phenomena, and invites a direct com- 

 parison between the two. 



The only experiments that have been undertaken to test directly 

 this question are the recent ones by Mathews'^ on certain hydroids 

 and on the tail of Fundulus. The interesting results reached by 

 Mathews, while leaving the problem, so far as the main issue is 

 concerned, still an open one, showed the importance of .further 

 examination of the subject. Mathews avoids, it is true, making 

 a direct comparison between physiological "polarity" and the 

 polarity present in electrical phenomena, and speaks rather of the 

 rate of growth of certain regions in comparison with others; but 

 if there is in reality any fundamental relation between the phe- 

 nomena in question, we should expect to find some expression of 

 it in the polar, or, more generally, the stereometric relations of 

 the parts. 



If, for instance, the development of a head at the anterior end 

 of a piece and of a tail at the posterior end is connected with dif- 

 ference of potential in the two regions, we might hope to get evi- 



iRlectrical Polarity in the Hydroids. A. P. Mathews. Am. Journ. Physi- 

 ology, Vol. VIII, No. IV, Jan. i, 1903, pp. 294-299. 



