338 



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



found to be the case as shown in Table V. in the great majority 

 of cases. The small size of the worm did not permit the testing 



TABLE V. 



ELECTRICAL DIFFERENCES BETWEEN ABORAL AND ORAL POLES OF THE CTENO- 



PHORE Plcurobrachia, ANTERIOR AXD POSTERIOR LEVELS OF Planaria 



maculata, AND ANTERIOR, MIDDLE, AND POSTERIOR LEVELS AND 



MARGINS OF A POLYCLAD. 



Ab., aboral ; or., oral; ant., anterior; mid., middle; post., posterior; mar., 

 margin ; rd., galvanometer readings. Reversed, reversed during test. Nega- 

 tive and positive refer to direction in the galvanometer. 



of more specific regions of the body ; it is possible merely to place 

 the electrodes on general anterior and posterior levels. The lack 

 of potential difference in Nos. 2, 3, 8, and 17 is probably due to 

 the circumstance that in these individuals the susceptibility of the 

 posterior end was practically equal to that of the anterior end. 



Of the polyclad mentioned above only seven specimens were 

 available. In all of these the anterior end was negative (galv.) to 

 the middle ; in most of them the posterior end was also negative to 

 the middle (this reversed while being tested in No. 4), and in the 

 four cases in which the matter was tested the margins were nega- 

 tive to the middle (Table V.). 



