FINE^STRUCTURE 33 



tips of the end fibers together without necessarily compacting the 

 membranelles. 



Neresheimer (1903), Schroder (1907), and Dierks (1926a) all 

 maintained that the basal lamellae were to give solidity and support 

 as anchors for the powerfully beating membranelles. It is difficult 

 to see how much support could be given because the membranellar 

 band is easily sloughed in salt solutions and when it comes off 

 there is no sign of supporting structure below the membranelles. 



Schuberg denied a muscular function for the basal fiber since 

 it is thrown into convolutions when the animal is contracted and 

 he thought that the basal lamellae could achieve little anchoring 

 in a fluid endoplasm. He suggested a nutritive function for the 

 parts he described, though granting there was still no proof of 

 this. The membranelles start and stop together and they beat in 

 an orderly fashion, one firing after the other in regular series to 

 produce a metachronal rhythm. It therefore seemed to Johnson 

 that the basal fiber with its connections to the membranelles would 

 be suited to a coordinating function. But even this reasonable 

 interpretation is not without its difficulties. Neresheimer found 

 that the usual nerve anaesthetics had no effect on ciliary action in 

 Stentor ; and also, if the membranellar band is severed deep into 

 the interior, metachronal rhythm continues on both sides of the 

 cut although the basal fiber must certainly have been sundered. 



The wide, clear marginal stripe of the frontal field running 

 along the inner margin of the membranellar band should not be 

 overlooked as a possible site of fibers coordinating the membranellar 

 beat. Clear stripes elsewhere carry fibers connecting the cilia, and 

 in Stylonychia the membranelles of the oral region are apparently 

 connected by a lateral fiber (Chen, 1944). 



Although the electronmicrographs give no indication thereof, 

 the membranellar band shows an intrinsic polarity. Bands or 

 sections of bands similarly oriented will readily join and mend 

 together without a break but not otherwise, and reversed mid- 

 sections of a band are reincorporated only after they, invariably, 

 rotate 180° in reorientation. This polarization appears during 

 primordium development. The primordium can be cut through 

 transversely in many places without effect, the severed parts merely 

 heahng together ; but if a sector is cut out and replaced in reversed 

 position it develops separately (see Fig. 41K). 



