Role of Preformed Structure in Cell Heredity 217 



RNA's. Their triplets appear to be capable of uniting effectively with 

 their complementary triplets in messenger RNA only after the trans- 

 fer RNA's have combined with their amino acids. Otherwise the mes- 

 senger could be clogged with blanks. In like manner, one may suppose 

 that the gene products which unite with molecules of the cortex ac- 

 quire specific activities as a result of the union. The various develop- 

 mental and genetic events which are regionally localized in different 

 parts of the cortex may thus be dependent upon specific molecular 

 combinations between newly formed molecules deriving from the 

 genes and preexisting molecular patterns already present in the cortex. 



This conception further agrees with the contemporary view that 

 function is intimately connected with molecular structure. Preexisting 

 structure determines processes that lead to different structures and 

 different processes in sequences that are self-determined at every step 

 and that lead back cyclically to the starting point. This dynamic 

 interplay of structure and process contrasts with the static view of an 

 unchanging, persistent, fundamental ground substance or organization 

 of the cytoplasm which always underlies the developmental and regen- 

 erative capacities of the cell (Calkins, 1926b: Ephrussi, 1952; Faure- 

 Fremiet, 1950; 1954; Harrison, 1945). Present knowledge rather 

 indicates a cyclically changing scene dependent at every level on pre- 

 existing structure, from the preformed enzymes and rihosomes that 

 are indispensable for genie replication and action to the organized 

 cortical fields, gradients, and localized inductor-response systems re- 

 quired for morphogenesis and hereditary transmission of cortical 

 structure and action systems. 



At this stage in discovery, we can only formulate the systems in 

 such general terms. The much more difficult task for the future is to 

 define and specify in molecular terms the decisive structures, gra- 

 dients, and inductor-response systems and to reveal how specific ab- 

 sorption, orientation, and activation of migratory molecules leads to 

 visible morphogenesis and genetic stability of cell organization. 



References 



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 J. Exp. Zool, 41:191-213. 



( 1926a ) . Biology of the Protozoa, Lea & Febiger. Philadelphia. 



(1926b). Organization and variation in Protozoa. Sci. Monthly, 22:341-351. 



Chatton. E. (1921). Reversion de la scission chez les Cilies. Realisation d'individus 



distomes et polyenergides de Glaucoma scintillans se multipliant indefiniment 

 par scissiparite. Compt. Rend. Acad. Sci., 173:393. 

 , and A. Lwoff (1930), Impregnation, par diffusion argentique, de Tinfracilia- 



