102 



Scientific Proceedings (99). 



lattice-work in the anteriorly projecting oral lip appears to be 

 connected with this fiber. Running posteriorly from the motor- 

 ium five distinct fibers diverge posteriorly, one each to the five 

 posteriorly located anal cirri. No such fibers pass to the other 

 thirteen cirri, but radiating fibrils from the base of each disappear 

 in the adjacent cytoplasm. There is thus an integrated fibrillar 

 system connecting the presumably sensory anterior lip, the power- 

 ful motor oral membranelles and the five major cirri of the ven- 

 tral surface most active in the walking and swimming movements 

 of the animal. 



Structural relations do not indicate a supporting or skeletal 

 function for these fibers. Observation of the fibers of living animals 

 with moving cirri, and of the course and diameter of the fibers 

 stained intra vitam and after fixation, showed not the least trace 

 of contractility in any of the fibrillar components of the system 

 except in cirri and membranelles. 



The movements of Euplotes fall into two main categories, first 

 creeping on the cirri, either (1) straight ahead, or (2) a quick 

 backward movement, or (3) a turn aborally to the right ; and sec- 

 ond swimming movements of six types, (1) forward without spiral 

 revolutions, (2) forward with spiral revolution, (3) circus move- 

 ment to the right, (4) circus movement to the left, (5) sharp turn 

 to the right, and (6) rapidly backward without revolutions. 



Cutting experiments in which the anterior fiber or the anal 

 fibers were severed were made to test the effect of cutting upon 

 coordination, as revealed in these stereotyped modes of behavior. 

 It is evident from transections of the body and excision of parts 

 that the frontal cirri or anal cirri are indispensable to normal 

 creeping movements, that the adoral membranelles are largely 

 responsible for swimming movement (3), that the anal cirri func- 

 tion chiefly in the performance of creeping movement (2), and swim- 

 ming movement (5), and that the adoral membranelles and anal 

 cirri cooperate to effect swimming movement (6). 



Cutting the membranelle fiber results in conspicuous differ- 

 ences in the behavior of the adoral membranelles on either side 

 of the incision and in abnormal spiral revolutions in swimming. 



Severing the fibers to the anal cirri affects both creeping and 

 swimming. Creeping movement (2) is infrequent. Swimming 



