182 SESSION II. DISCUSSION 



L. Pauling (U.S.A.): 



It is easy to understand why organisms arc built up of optically active molecules. The 

 more complicated molecules are asymmetrical, they exist in both laevorotatory and 

 dextrorotatory forms. Living organisms have the ability to create specific molecules with 

 the help of matrices. In doing so the matrix for a L-molecule cannot possibly be used for 

 the synthesis of a D-molecule. Thus, if we wished to have a racemic organism which 

 would produce both L-organs, i.e. L-molecules, and D-molecules, it would have to contain 

 two collections of matrices, two collections of genes — one dextrorotatory and one laevo- 

 rotatory. The course of events depends, however, to a considerable extent on chance. In 

 living organisms chance separates these two collections. They are completely independent 

 of one another and it would not be logical to expect that both should have developed in 

 exactly parallel ways side by side giving rise to corresponding organisms, i.e. duplicating 

 the mechanism with which L-organisms and D-organisms would each, separately, be 

 endowed. 



J. D. Bernal (Great Britain): 



I should like to make an observation about the paper to which I listened this morning 

 concerning the action of radiation in the extreme ultraviolet on the synthesis of small 

 molecules, as this paper throws new light on the hypothesis as to the important part played 

 by clays and other mineral substances in the emergence of life. 



When I postulated the implication of these mineral substances in the scheme of bio- 

 genesis I was thinking of their adsorptive powers, which would lead to an accumulation 

 of organic substances on their surfaces. Later on, though I had no proof at that time, I 

 put forward the suggestion that they might have a catalytic action about which Prof. 

 Akabori will speak later. Today we have heard of yet another phenomenon, namely the 

 extension of the limits of absorption towards the long-wave ultraviolet range, for those 

 molecules which are adsorbed on such surfaces. I should like to make it clear here how 

 I envisage the action of such substances on the surface of the Earth. 



I imagine that adsorption, for the most part, took place on minerals of secondary 

 origin. The clayey minerals which we meet in the soil do not appear to be the direct 

 products of weathering; they are formed by precipitation of solutions of alumina and 

 silica. This has been demonstrated by experiment. In this way we get aluminosilicates 

 and their porous polyhydrates, which were certainly produced abiogenically in the early 

 stages of the formation of the crust of the Earth, in association with the circulation of 

 water. Together with them we also find iron hydroxides. The places where they were 

 formed were beds of mud. 



Beds of mud have two important properties. In the first place, considered vertically 

 they form columns, that is to say they allow dissolved material to pass through them, as 

 through a chromatographic column, they modify various reactions and separate the 

 reagents into different zones. In the second place, the way in which beds of mud are 

 formed is such that they are periodically covered by new layers, perhaps daily, perhaps 

 whenever it rains. 



This means that a reaction which leads to the formation of many substances is diverted 

 towards the production of substances which are sorbed. The adsorbed material is removed 

 from the sphere of the reaction and the reaction is diverted towards its synthesis. In 

 other words, beds of mud constitute an apparatus for the utilization of material. However, 

 if this were the whole story, it would not lead to the formation of substances but to their 

 disappearance. In this connection I believe that a. great part was played by the second 

 factor, i.e. the fact that beds of mud are continually accumulating layer by layer and that 

 the accumulated material again enters into circulation through stream erosion. 



It seems attractive, at first sight, to suppose that the original synthesis occurs at great 

 depths in pure water. On beds of mud, synthesis occurs only in the superficial layer, 

 i.e. in a layer less than i mm thick. This layer is constantly being renewed and seems very 

 likely to provide suitable conditions for polymerization. 



In conclusion, I should like to make a general comment. From the physical aspect, 

 the process of biogenesis is very like the colloidal process of synaeresis, in which the 

 original watery medium separates out from the colloids. In the early stages this process 

 may have been purely physical, making use of colloidal mineral substances, but later it 

 became the very complicated synaeresis which we sec in the evolution of biological 

 forms. 



