258 The Nature of Biological Diversity 



in the acting out of these various and sundry programs, the entire 

 community of cells will he paced and coordinated hy certain endog- 

 enous molecules which, as endocrine agents, will give stop-and-go 

 signals reminiscent of the "controlling elements" in hacterial systems. 

 It is clear that the programming of cells has to do with sequential 

 gene action — the "taping" of the individual cells for a subsequent 

 "playback." In the concrete case of the higher insects, it is a process 

 that anticipates the future of the individual life and predicts with 

 utmost precision the chemical engineering of larva, pupa, and adult. 



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