ORIGIN OF LIFE ON THE SHORES OF THE OCEAN 113 



synthesize protein and contain ribonucleic acid, and the deoxyribo- 

 nucleic acid-containing chromosomes. It may well be that all 

 these represent specialized versions of what was originally an 

 all-in living molecule. This is not the type of living molecule that 

 Oparin attacks, I think quite rightly, because this is essentially 

 a complex of molecules having between them all the necessary 

 functions, not the simple, naked nucleic acid molecule which can 

 do nothing by itself. On the other hand, it may very well be that 

 in the general symbiosis of the more primitive mud stage, these 

 elements developed separately and only came together as a kind 

 of enclosed symbiosis containing all the elements out of which 

 cells are made. 



To complete the picture, only one further thing is required, 

 namely the development of some means of blocking off the cell. 

 The coacervates of Oparin are unenclosed — small molecules could 

 diffuse in and out of them as well as right through them. In 

 consequence, all chemical processes occurring in them must be 

 done in common; the greatest isolation that can be maintained is 

 due to the gradients of concentration of one chemical or another. 

 However, there is one group of organic molecules, the lipids, with 

 long molecules that pack together in sheets, which are able to 

 supply just those outer and inner partitions which are necessary. 

 I think that the appearance of lipids made possible, first of all, a 

 separation between the original coacervate and its environment, 

 making it effectively a little box or cell, and then the separation 

 of the different parts of this internal structure from each other. 

 One part could become a nucleus containing essentially the 

 memory elements needed for regulation and reproduction, and 

 another part could contain the mitochondria for the metabolic 

 processes, and so forth. The new knowledge of the cell gained by 

 the use of the electron microscope shows it as not just one single 

 city surrounded by a wall, the old cell wall that we have talked 

 about for eighty years or more, but as a whole country including 

 many cities and villages, each with its different capacities and, as 

 it were, trading with each other. This latter evolution, however, 

 falls outside the scope of this paper. 



To sum up, what I feel is that we now have the skeleton of a 



