Structure and Polarity of Electric Motor Nerve-Cell in Torpedoes. 239 



25 and 30, we find fish that were killed without electrical activity and 

 show 99 and 95 per cent of ventral orientation respectively. Other 

 experiments not recorded here have also shown that the fish which die 

 quickly do not always show a general or central distribution of the 

 plasmosomes. 



The third condition can now be discussed, namely, that this orienta- 

 tion of the plasmosome is a permanent condition. To arrive at a con- 

 clusion it must be shown that there are no temporary movements of 

 the plasmosomes during the electrical activity of the fish. 



Fresh slices of the electric lobe were cut with a Valentine's knife in a 

 vertical direction and after being covered and put under an immersion 

 lens they were subjected to electrical and other stimuli that would 

 have been sufficient to cause their discharge in a living fish. While 

 thus being stimulated they were closely watched and it was noted 

 that no movements of the plasmosomes occurred. 



The fact that the plasmosomes exhibit a widely differing percentage 

 of orientation in different individuals and that this percentage appears 

 to be the same in all parts of the electric lobes of each individual might 

 also seem to indicate that there were no temporary movements of the 

 plasmosome. This has been further controlled by observing both fresh 

 material as mentioned above and different fixations of the same speci- 

 men, after further stimulation followed by fixation and sectioning. Thus 

 No. 10 was killed with the knife and fresh material was at once put 

 under the microscope, where it was determined that the percentage 

 of ventral orientation was 5 per cent. This was a very weak ventral 

 orientation, so the remaining tissue, still capable of physiological action, 

 was further stimulated both mechanically and electrically and then 

 bits were fixed and sections cut. These preparations showed no 

 futher orientation, so it was concluded that the excess stimulation had 

 not moved them, and since this stimulation was applied to cells that 

 were not ventrally oriented, and in which there was still room for 

 orientation, this was considered to be strong proof that there is no 

 ventral movement during the nerve activity which results in the 

 electric discharge. 



Another strong point must be considered at this time. Magini 

 erroneously assumed that the functional axis of these cells lay in all 

 cases in a dorso-ventral direction, with the implantation cone and neu- 

 raxis on the ventral side of the cell (text-fig. 4) ; and he therefore states 

 in some places that the plasmosome (nucleolo) moves ventrally, and 

 in other places he states that it moves toward the origin of the neuraxis. 

 The writer, as stated in the description of the cells above (page 216), has 

 found that a certain number of cells in each electric lobe, about 20 per 

 cent of them, are so situated that the neuraxis leaves in a lateral or 

 even in a dorsal direction (text-fig. 5) , and that in these cases the plas- 

 mosome acts in accord with the majority of usual cases, i. e., those with 



