No. 4S9] THE STRU 



The generally accepted tin 



of essentiaiK tlic ^-auw \vnv 

 toplasinic sheath which end- 

 Primitively the sheath ( Fiu'. ' 

 not marked oil' stnicturallv 

 of the ectopla^n. .-eeondai 

 into contractii.'aiHl imneoiitr; 

 areslKHM. in the l\.llnu i,m <.\- 

 (Fig. 2, g) of velar cili;. a 

 confined to the hase of 

 reversible cilia (Fig. 2. / ! tin 

 two opposite bands w hich in 

 sides of the supporting axis, 

 more strongly than the other { 

 but certain organic and inor< 



