MICRODISSECTION STUDIES 125 



the passage of the metachronal waves, and that new waves 

 and a new rate of beat start in the region immediately distal to 

 the cut. When the cut healed — in 15 min to an hour or so — the 

 metachronal waves passed across the cut place as if a cut had 

 never been made. Similar cuts across the ciliary rows of Opalina 

 also obstruct the passage of metachronal waves, but the reversal 

 response still occurs simultaneously on the two sides of the cut 

 (Okajima, 1954a). The same results have been reported by 

 Doroszewski (1958) in Paramecium. These observations confirm 

 the findings of Worley (1934) in similar experiments on the body 

 cilia of several ciliates. Taylor (1920) has investigated the effects 

 of cutting the fibrils which connect the cirri and membranelles 

 of Euplotes to the *' motorium "; such cuts result in disorganiza- 

 tion of the movements of these organelles, and it was therefore 

 concluded that the fibrils function as conductors. 



It seems fairly certain that the normal direction of ciliary beat, 

 at right angles to the line through the two central fibrils, is 

 determined in the formation of cilia, and that it remains 

 unchanged throughout life, with the exception of periods of reversal 

 where these occur. This conclusion comes from experiments in 

 which areas of ciliated tissue have been cut out and grafted back 

 into position with reversed polarity. Using this method, von 

 Briiche (1916) found that cilia continue to beat in the same 

 direction relative to their own basal protoplasm, and not relative 

 to their new position. Lucas (1933) also found this to be true 

 provided that the environment was unaltered. It is possible that 

 the orientation of beat is not fixed immediately the cilia are 

 formed, for Twitty (1928) found that while the cilia of the 

 epithelium of very young amphibian embryos could change their 

 beat direction to correspond with that of cilia of the surrounding 

 region, the cilia of older embryos retained their polarity so that 

 cilia of the graft beat in the opposite direction to those of the 

 surrounding area. 



This expression of polarity may be shown even more strongly 

 by the grafting of some ciliated tracts in reversed orientation. 

 Thus Tartar (1960) found that if sections of the membranelle 

 band of Stentor are reversed, then proper reuniting of the section 

 will only occur after it has turned itself back through 180°. The 

 whole membranellar band then resumes a co-ordinated beat. 



