Structure and Polarity of Electric Motor Nerve-Cell in Torpedoes. 247 



The next experiment, on torpedo No. 3, was positive in its results. 

 The force used was 543 times gravity for 1 minute. The plasmosomes 

 were all moved by an anterior-posterior centrifugal force of this strength 

 from varying positions, mostly ventral, to a position in a posterior arc 

 of about 40 degrees. (See text-figure 6, zg.) In this arc the nuclear 

 wall is so flat with respect to the direction of the force exerted that it 

 makes very little difference in what portion of such an arc a plasmosome 

 comes to rest, just as the natural force of orientation always brings it 

 into the arc xy (text-fig. 6), but into any part of that arc. Thus, in 

 text-figure 6, we have a diagram representing the outline of a nucleus of 

 one of the electric motor nerve-cells with one arrow representing the 

 direction of the force of 

 gravity and another rep- 

 resenting the centrifugal 

 force as applied in this 

 experiment on No. 3, as 

 well as in other ex- 

 periments where greater 

 forces were employed. In 

 such a cell the normal po- 

 sition of a naturally ori- 

 ented plasmosome is at 

 1-a, although it may rest 

 in any part of the arc xy, 

 as at 1-6 or l-c. When 

 centrifugal force is ap- 

 plied of sufficient extent 

 to change the position of 

 the plasmosome it moves 

 in the direction indicated 

 by the two-barbed arrow 

 until it comes to rest on 

 the arc zg. If the plasmosome starts from 1-a, or even from a more 

 dorsal position, as 3-a, it will come to rest well in the ventral part of 

 the arc zg or at 2-a. In this case it rolls along the curved outline of 

 the nucleus until the first part of the arc is reached at g, when it stops 

 because the angle is too obtuse. If it starts from a median position, 

 as at 3-6, or from any position on a median line with reference to the 

 centrifugal force applied, as at 3-e or 3-/, it will come to rest in the 

 center of the arc zg at 2-6. If it lies in the dorsal half of the nucleus 

 as at 3-d or 3-c it will be located by the centrifugal force at 2-c. 



Thus it becomes very easy to estimate the percentage of the central 

 orientation of the plasmosome, even after centrifugal force has been 

 applied at right angles to gravity and the plasmosome has been re- 

 oriented by this new factor. Ventrally oriented plasmosomes will 

 become located in the ventral portion of the centrifuged mass of chro- 

 matic material as indicated in text-figure 6. 



FIG. 6. Diagram showing arc in which the plasmosome 

 will not move when it arrives from any part of 

 the nucleus. 



