1920] Taylor: Neuromotor Apparatus in Euplotes 451 



This fibrillar system is not contractile in function. — The contrac- 

 tility either of cirri or of membranelles is not conditioned upon their 

 attachment to the body and consequently not upon any mechanism 

 within the body. All the frontal, ventral marginal and anal cirri and 

 membranelles have distinctly been observed to continue contractions 

 for a considerable period after their detachment from the body. These 

 reactions have already been discussed somewhat at length, and need 

 not be further elucidated here. It is now only worth while to empha- 

 size that their capacity of contraction inheres within these external 

 organelles themselves. Whether this contractility is effected by the 

 basal corpuscles, the axial filament of the component cilia, or the 

 plasmic sheath enclosing the filaments, is not for our consideration. 



The loose attachment of the basal plate to the fiber plate indicates 

 that the fibrillar system differs both in structure and in function from 

 the contractile, external organelles. The ease and completeness with 

 which the basal plates become detached from the fiber plates and the 

 want of evidence that the ciliary rootlets and fiber plate are more 

 than merely contiguous structures are significant features supporting 

 this conclusion. 



The consistency of the anal cirri fibers and their feeble attachment 

 to the ectoplasm and to the easily displaced motorium would suggest 

 their meager effectiveness in functioning as contractile structures. 

 The fibers tend to remain straight when undisturbed. They do not 

 become kinked or curled upon the disintegration of the ectoplasm. It 

 is only by means of the needle or some other external agency that they 

 may readily become distorted. They may be pulled in two with the 

 needle-point but at no time have they shown any indications of 

 stretching. 



The reversibly effective strokes of the anal cirri preclude the possi- 

 bility that, the anal cirri fibers are contractile in function. The four 

 effective strokes of these cirri have been described in foregoing para- 

 graphs. These are: (1) directly backward strokes parallel to the 

 sagittal plane. (2) directly forward strokes parallel to that plane, 

 (3) laterally backward strokes hardly parallel to the frontal plane, 

 and (4) similar lateral strokes directed forward. All these strokes 

 have been seen many times in the anal cirri of a transected posterior 

 piece as well as after an incision which had clearly severed the anal 

 cirri fibers. Since contractile fibers can operate effectively only in 

 one direction, it is inconceivable that an anal cirri fiber can function 

 as a contractile organelle. 



