m?m^k 



PLATE IV. Ribonucleoprotein particles (RNP) from E. coli. 100,000 X- (o) RNP particles from a 

 30-s preparation. The arrow indicates a typical asymmetrical particle. (b) RNP particles from a 

 50-s preparation, (c) RNP particles from a 70-s preparation. These specimens also show 30 and 50 s 

 particles. The 70 s particles, such as are indicated by arrows, show a substructure indicating double- 

 ness. (d) RNP particles from a 100-s preparation. The 100 s particles are dimers of the 70 s. (From 

 Hall and Slayter, 1959, J. Mo/. Biol., 1:329.) 



