178 CELLS, TISSUES, AND ORGANISMS 



the apparatus for division. In short, one feels that the central trend of 

 contemporary molecular biology, concerning which others have spoken 

 at this symposium, is not a fad or a bandwagon idea exploiting the 

 aesthetics of oversimplification but is genuinely the foundation for the 

 study of the progress of the cell as a whole through time. 



The complexity of the plan of cell reproduction that I have been 

 discussing is not that of a rigidly integrated system, which collapses 

 when we tamper with one element. To a surprising extent, the com- 

 plexity involves a system of parallel processes which may be dissoci- 

 ated from each other and which may proceed in a different order in 

 different kinds of cells. It may be more difficult in the end to understand 

 this flexible integration of processes which are not rigidly interdepend- 

 ent, but this is the problem, characteristically biological. We shall cer- 

 tainly have to pay more attention to the timing mechanisms of events 

 in the cell cycle, but this becomes possible now that a little more is 

 known about the control of the qualitative and quantitative character 

 of cellular processes. 



Finally, it must be said that the plan we have been considering 

 was addressed to the reproduction of the "higher" kinds of cells, those 

 of plants and animals. It may not apply at all to bacteria and some other 

 groups of microorganisms. Many of the special features of the plan are 

 governed by the exigencies of chromosomal and mitotic mechanisms, 

 and we are forewarned by a number of recent discoveries in micro- 

 biology that the reproductive equipment may be organized, differently 

 in bacteria. 



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Brachet, J., 1957. Biochemical Cytology (N. Y., Academic Press). 



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