I 020 ] Taylor: Neuromotor Apparatus in Euplotes 437 



for long periods. Its oral lip is more sensitive to a stimulus by the 

 needle-point than are the membranelles over the oral lip, or its pos- 

 terior, cut surface, or the frontal cirri or any. other part. 



The posterior part is generally very much less active. However, in 

 ten recorded instances this piece revolved on its cut surface as an axis 

 exceedingly rapidly (about two revolutions per second) for a half 

 minute or less just after the transection was completed. This revolv- 

 ing performance, generally at a much slower rate, is a common reaction 

 of the posterior piece following this operation. The direction of these 

 revolutions is clockwise when viewed from the left side. For some 

 time after the cut is made the anal cirri are quite active with their 

 effective stroke in such a way as chiefly to induce the revolutions. This 

 part swims in circus movements to the right infrequently and very 

 seldom rotates on the long axis; when it does so, it moves quite 

 clumsily and imperfectly. "Within about an hour movement ceases. It 

 is then much less responsive to mechanical stimuli than is the anterior 

 part, after coming to rest. "When thus stimulated its movements, which 

 are for the most part revolutions, are effected chiefly by means of the 

 two ventral and the two right, fimbriated marginal cirri, the anal cirri 

 remaining more or less passive. 



Experiment 209 (fig. 3). — Anterior part swims violently in various devious 

 movements, sometimes rotating on the long axis or reversing to swim a short 

 distance backwards, but most of time it moves in right circus movements. This 

 ceaseless swimming continued from 11:50 a.m. until about 5 P.M., when its move- 

 ments were considerably slower, and at 5:30 p.m. the part was resting on debris. 

 Readily responded to touch of the needle point against the oral lip, but less so 

 when the adoral membranelles, frontal cirri or posterior cut surface was simi- 

 larly stimulated. Slight jarring induced violent swimming, which lasted about 

 thirt}' seconds, after which it again became quiet. At this time rotation on the 

 long axis was more common than previously. Following morning, this part had 

 died. 



Posterior part not very active from the first. Anal cirri beat slowly, irregu- 

 larly and with little effectiveness. Occasionally swam in circus movement to 

 the right and sometimes showed imperfect rotations on the long axis, but more 

 often its movements were revolutions about the cut surface as an axis. Within 

 forty minutes, it had become passive, the two right marginal cirri infrequently 

 showing movements which were always infundibular but without effect. Only 

 slightly responsive to jarring, then generally revolved as before but very few 

 times, after which it again became quite inactive. These revolutions were 

 effected mainly by the two right, fimbriated marginal cirri with infundibular 

 movement; the two on the left lashed with the effective stroke upward, thus 

 inducing the revolutions. The two ventral cirri were active most of the time, 

 also showing conspicuously the infundibular type of movement. The anal cirri, 

 on the other hand, were mostly inactive; irregularly one or two might lash 

 feebly, but never more than one at a time. Their effective stroke was always 

 backward, therefore tending to aid the part in its rotations clockwise as viewed 

 from the left. This part also died within about thirty-six hours. 



