PROTOZOA AS CELLS 51 



reported by Seaman (1960), who employed a detergent for pro- 

 gressive solubilization of alcohol-killed cells of Tetrahymena. He 

 was able to isolate large populations of uniform tiny particles that 

 appear to be kinetosomes, although confirmatory electron- 

 microscope examination of sectioned pellets has not yet been 

 made. Comparison of the presumed kinetosomes with whole-cell 

 extracts showed a significantly higher proportion of protein in 

 the former (49-6 per cent dry weight versus 164 per cent in 

 whole-cell extracts), less lipid and carbohydrate, and, most 

 significantly, a much higher DNA :RNA ratio (1 -5 in kinetosomes, 

 0-1 in whole cells), although total nucleic acid content was similar 

 in both. Measurements of enzymic reactions showed a consider- 

 ably greater specific activity in the kinetosomes than in whole-cell 

 extracts for glycolysis, oxidative phosphorylation, apyrase, 

 succinic dehydrogenase, and fumarase. In preliminary cyto- 

 chemical studies, Randall and Jackson (1958) and Randall (1959b) 

 reported the demonstration of DNA and RNA in kinetosomes of 

 Stentor, Tetrahymena, and two metazoan epithelia. 



An understanding of the structural chemistry of the nagellum 

 and kinetosome will constitute a great leap forward, but thus far 

 such efforts have provided no clues to the reason for the 9/9 -j- 2 

 pattern. Beyond recognizing that the fiber number and arrange- 

 ment represent a functional necessity for kinetosomes/centrioles 

 as well as for flagella, we have not progressed appreciably in this 

 direction since the early speculations of Manton (1952, 1956), 

 Astbury, Beighton, and Weibull (1955), and Bradfield (1955) (see 

 also Serra, 1960). Although the skewing of doublet and triplet 

 fibrils, the attachment of additional fibrous structures to the 

 kinetosome-centriole, and the one-way orientation of arms on 

 the peripheral fibers all confer a fundamental asymmetry on these 

 bodies, there is superimposed a bilateral symmetry in the flagellum 

 itself, as Manton (1952, 1956) has pointed out. Careful study of 

 the arrangement of spines and mastigonemes relative to the 11 

 axial fibrils in some phytoflagellate flagella has led her to conclude 

 that the plane of symmetry passes between the two central fibrils 

 and bisects one of the nine peripheral fibrils. Mastigoneme rows 

 are disposed symmetrically on the two sides. Fawcett and Porter 

 (1954) noted that, in the molluscan gill epithelium they were 

 studying, the two central fibers appeared to have a consistent 



