THE PLAN OF CELLULAR REPRODUCTION 161 



In this case, only A is self -reproducing, and it contains the information 

 necessary for the generation of elements b to z. 



It is easy enough to understand why the reproduction of a plant or 

 animal is a generative process. It would be grotesquely complicated for 

 all of the molecular elements of a human being to replicate and sort 

 themselves out into two human beings. The mysteries of the actual 

 process whereby the chromosomes reproduce themselves, some going 

 into gametes which in turn generate new complete individuals, seem 

 simple by comparison. In any event, that is the way the reproduction 

 of very complex systems goes: by a sequence of conception, develop- 

 ment, and parturition. In cell reproduction, the replication of the 

 genetic system provides the conditions for doubhng the cytoplasm, 

 after division, wliich in turn makes further division possible ( Figure 1 ) . 

 The whole cycle contains the elements of conception, development, and 

 parturition. A complete bacteriophage particle reproduces generatively; 

 its DNA replicates itself and directs the synthesis and assembly of tlie 

 protein constituents of the "soma" of the virus particles, these not 

 being produced by self -replication. 



The only examples of replication by a fission process that we can 

 cite involve the replication of molecules, nucleic acids, or nucleopro- 

 teins. It is conceivable that the fission scheme is restricted to molecu- 

 lar dimensions. If not, we must discover a mechanism of coding in two 

 or three dimensions (Danielli, 1958) to supplement the contemporary 

 ideas about coding through one-dimensional sequences. If generative 

 reproduction prevails at all levels higher than the ultimate molecular 

 sources of information, we may not need to face such coding problems, 

 substituting for them problems of directed synthesis and assembly. 



CELL ^^ 



Abc.z) -^ 



(Abczj 



Figure 1. The scheme of cell reproduction, viewed as a form of generative 

 reproduction. The genetic material (A) directs the production of the various 

 cell constituents b z and also reproduces itself. 



