222 CILIATE FIBRILLAR SYSTEMS 



interpretation, viz., that some of the few fibrils of other cirri in this 

 species were not ahgned longitudinally, but might be even transverse to 

 the longitudinal axis. 



Griffin based his concept of contractility for these fibrils in E. Worces- 

 ter/ only partly, however, on this comparison with myonemes in other 

 ciliates. He accepted Biitschli's interpretation of a contractile function 

 for the marginal and anal cirri fibrils in Stylonychia as a much more 

 reasonable view, and also noted that "Every detail of arrangement and 

 structure indicates that the fibrils are, principally at least, contractile in 

 function." He observed, also, that the fibrils were developed around the 

 bases of the cirri in such a way as to assist in producing the ordinary 

 motions. "As the anal cirri have only a single strong motion, a vigorous 

 kick directed backward, each needs but a single strong fibril." 



Evidently Griffin had not seen any reversal in the effective stroke of 

 these anal cirri. In several other species of Euplotes this reversal is not 

 uncommon in both swimming and creeping movements. Should that be 

 the case in E. tvorcesteri, then a contractile function for the anal cirri 

 fibers is scarcely conceivable. The effective function of a contractile fibril 

 is obviously a pulling but not a pushing function. Moreover, Prowazek's 

 account of the contractile behavior of the anal cirri in E. harpa, cited 

 above, largely vitiates any claims for contractility in the cirri fibrils of 

 this species, and similar behavior has been observed by the writer in the 

 anal cirri of E. patella. It was also noted (Taylor, 1920) that cutting 

 these fibrils apparently did not impair the effective stroke of the anal 

 cirri, whether that stroke was directed backward or forward. 



The latter evidences were thus cited against the assumption that these 

 fibrils in E. patella were contractile. It was further shown by those 

 experiments that cutting the anal cirri fibrils interrupted the coordinated 

 movements between anal cirri and adoral membranelles. Also, severing 

 the membranelle fiber likewise interrupted the coordinated movements 

 of the membranelles on opposite sides of the incision. Incisions in other 

 parts of the body did not impair the coordination of these organelles. 

 It should be pointed out, however, that those incisions which did inter- 

 rupt coordinated movement of organelles cut not only the anal cirri 

 fibrils or the membranelle fiber, but also the peripheral fibrils which 

 have since been described especially by Turner (1933). Whatever role, 

 if any, these peripheral fibrils may have in E. patella's coordinated 



