452 University of California Publications in Zoology [VOL. 19 



The fibrillar system in Euplotes patella does possess properties of 

 conductivity functioning to coordinate the movements of the external 

 organelles with which it is associated. Normal, coordinated activity of 

 the series of membranelles is effected through the motorium, the mem- 

 branelle fiber and its attached inrmbninelle plates. An incision at any 

 point through the oral lip, which did not sever the membranelle fiber, 

 gave negative results. But when the membranelle fiber was severed, 

 there were conspicuous changes in rhythmic movements of the mem- 

 branelles on either side of the incision and distinct modifications in 

 the animal's swimming movements. It was stated that the mem- 

 branelles on the right side, whose fiber remained connected with the 

 motorium, at times became inactive and projected straight out from 

 their base ; only occasionally were they seen to move in apparent 

 coordination with those on the left side of the incision. The latter, 

 the fiber of which had lost its connection with the motorium, showed 

 continuous movements with their effective stroke mostly such as 

 normally tends to drive the animal forward. This tendency in the 

 rate of movement and in the direction of the effective stroke is com- 

 parable with the unchanging, ceaseless movements of the adoral mem- 

 branelles of the excised oral lip which continually moved in circuits 

 to the right and was never observed to reverse the effective stroke of 

 the adoral membranelles. This constancy in the behavior of mem- 

 branelles whose fibrillar connection with the motorinm is severed might 

 suggest that their usual modifications in direction of stroke and rate 

 of movement may in some way be effected through the motorium. It 

 is furthermore evident that the unusual swimming movements which 

 followed such incisions resulted from the severing of the membranelle 

 fiber. 



Efficient, coordinated behavior of the five anal cirri is effected 

 through the normal functioning of the five anal cirri fibers with their 

 attached fiber plates. The effects of severing these fibers at any one 

 of several regions (see Incisions, page 441, above) were distinct and 

 more or less constant. The infrequency and lack of facility in creep- 

 ing which was, at times, obviously initiated by the frontal cirri, and 

 the rare occurrence of the avoiding reaction were noteworthy changes 

 in the animal's creeping movements. But more evident were its 

 modifications in swimming. There was a marked tendency toward 

 performing circus movements to the right. Sharp turns to the right 

 were infrequent and in three cases at no time observed. The rapid, 

 backward, avoiding reaction has never been clearly identified after 



