1920] Taylor: Neuromotor Apparatus in Euplotes 429 



all the cirri to some extent but chiefly the anal cirri and adoral mem- 

 branelles, as experiments later will show. Movement 3 is affected also 

 with the aid of all cirri and aboral membranelles, but chiefly by means 

 of the frontal cirri, except when the turn is very rapid and through a 

 large angle, say 90 degrees; then all the cirri, but principally the 

 frontal and anal cirri and the adoral membranelles, are brought into 

 play. Creeping is rendered impossible upon excising the anal or the 

 frontal cirri. This feature will be described later under the head 

 "Experimental." 



Euplotes patella's swimming habits are less common than are its 

 creeping movements but the animal utilizes this special advantage by 

 no means infrequently. Also, the variety of its swimming movements 

 indicates considerable proficiency in this valuable mode of locomotion. 

 The six movements in swimming, above referred to, are as follows-. 

 (1) straight ahead without rotation, (2) straight ahead in spiral 

 rotation. (3) circus movement to the i-i Ljlit, without rotation, (4) circus 

 movement to the left, without rotation, (5) a sharp turn to the right, 

 similar to creeping movement (3), and (6) movement directly back- 

 wards, comparable with creeping movement (2). 



It will be convenient here to recall the special, effective strokes of 

 the membranelles and of the various groups of cirri : (a) The effective 

 strokes of the membranelles may pull the animal forward or by reversal 

 drive it backward. Without the interplay of cirri, the tendency of 

 direction by means of the membranelles is neither straight ahead nor 

 straight backwards but in a circuit, as will be shown later, (b) The 

 caudal cirri may function as rudders or as propellers. The two on the 

 right usually function as propellers; the two on the left, as rudders. 

 Griffin (1910), for the caudal cirri in E. u-orcesteri, finds the ten- 

 dencies of their movement to be just the reverse of those which I have 

 ascribed to corresponding cirri in E. patella, (c) The anal cirri may 

 lash directly backward, individually or simultaneously, and so drive 

 the animal forwards; or they may lash directly forward, not always 

 but often synchronously, driving the animal backwards; or they may 

 lash to the right side with the effective stroke backwards or forwards, 

 thus aiding to turn the animal to the left or right respectively. 

 (d) The frontal and ventral cirri commonly show infundibular move- 

 ment, with the effective stroke directed variously; only occasionally 

 has the lashing, whiplike movement been observed in these cirri. 



(1) The "straight ahead" swimming movement is of short duration, 

 but occurs rather frequently, particularly after the animal has been 



