444 University of California Publications in Zoology [VOL. 19 



by means of the needle-point produces modifications in the animal's 

 several movements which, so far as I have yet been able to ascertain, 

 do not differ markedly from the effects that follow severing the mem- 

 branelle fiber or the anal cirri fibers or both near the motorium, or 

 the anal cirri fibers at any point. There is, then, no certain evidence 

 from these experiments that the function of the motorium is more 

 specific than that of its attached fibers. These negative results may 

 be attributable, however, to faulty or insufficient technique. On the 

 other hand, the differences in the behavior of the membranelles on the 

 left and right sides of the incision severing the membranelle fiber, 

 which were previously described, might indicate there some role 

 peculiar to the motorium. 



Perhaps the clearest evidence for the want of coordination and of 

 concomitancy of movements between the membranelles and anal cirri 

 appeared in these incised animals upon supporting one of them against 

 the under surface of the cover-glass with a very flexible needle. To 

 the hanging drop had been added a trace of india ink or a carmine 

 solution ; thereupon, any changes in the direction of the effective stroke 

 either of the anal cirri or of the membranelles were quite conspicuous 

 in the corresponding movements of the particles of india ink or of 

 carmine. Infrequently the carmine granules were driven in the same 

 direction by the membranelles and by the anal cirri, and the effective 

 stroke of these organelles varied synchronously. This concomitancy 

 however, did not long continue. Their phases of rhythm, it would 

 seem, changed so that now while the membranelles were driving some 

 particles anteriorly, other particles were being driven posteriorly by 

 the anal cirri, or vice versa. These changes were conspicuous and 

 frequent. 



DISCUSSION 



These experimental studies have yielded some evidences on the 

 nature of organelle movement in Euplotes patella which are here 

 worthy of consideration. The significance of the general problem of 

 ciliary structure and movement, probably due to the prevalence of 

 cilia in both protistan and metazoan organisms, was early recognized 

 (Stuart, 1867) and has occasioned the writing of a large literature, 

 most of which has been reviewed by Putter (1903), Prenant (1914), 

 and Saguchi (1917) . Aside from minor modifications, the structure of 

 cilia, wherever found, appears much the same. A cilium is composed 



