SESSION I. DISCUSSION 117 



acting with other chemical substances, remaining like itself and beginning to be different 

 from itself. This factor of a qualitative break in Natvire associated with the emergence 

 of a chemical substance of such a kind that, in reproducing itself, it developed, is not 

 to be seen in the whole of the suggested scheme of biopoesis, starting with the simplest 

 organic molecules and finishing with cells. 



The scheme provides a correct and consistent materialist picture of the form of de- 

 velopment of nature but does not disclose the main point of these stages of development: 

 it does not reflect the transition from chemistry to biology. In other words, it does not 

 reflect the essential dissimilarity — the boundary between these two forms of the motion of 

 matter, one of which obviously precedes the other. 



It would also have been desirable for the scheme of biopoesis to have shown the specific 

 characteristics of life. 



J. D. Bernal (Great Britain): 



The concept of organic evolution cannot be applied logically to early stages of biopoesis 

 because it implies the prior setting up of a system of quasi-perfect reproduction. This is 

 now maintained by a genetic mechanism based on deoxyribonucleic acid. Before this 

 mechanism existed offspring could only have a rough resemblance to their parents and 

 every act of reproduction was a measurable step in evolution. The evolutionary staircase, 

 which consists of long runs of unaltered reproduction separated at intervals by sudden 

 mutations, must in its early stages have been more like an irregular ramp. 



Recent evolutionary Early evolutionary 



progress progress 



N. H. Horowitz (U.S.A.): 



Prof. Bernal and I appear to differ in our definitions of life. He considers as alive 

 chemical systems which I do not. I do not have time to elaborate on this difference of 

 opinion, but my reasons for preferring my own view were stated in my paper. 



N. W. PiRiE (Great Britain): 



Like some painters, Dr Horowitz seems to see life in the strong primary colours — or 

 even in black and white. I see more shades and so disagree with almost all his simpli- 

 fications. 



First he says he does not believe in a continuous transition between living and non- 

 living because he has not seen it. Nor has anyone else, because our idea is not that it still 

 exists but that it once did. As Darwin, TyndaU and others pointed out many years ago, 

 any eobiont that appeared now would be promptly eaten. 



