SESSION V. DISCUSSION 495 



which served as the factor permitting the development of complexes with many com- 

 ponents, demarcated from their surrounding medium without the formation of a definite 

 morphological limiting membrane. 



It was especially interesting to us to observe that these artificial structural formations 

 changed their shape when the composition of the surrounding medium was changed. 

 ThuSj they manifested mechano-chemical reactivity, i.e. they had such properties as 

 might serve as a basis for the emergence of irritability, which is a universal property of 

 protoplasm. It may be said that these systems already possessed irritability at a molecular 

 level. I should like to point out that the attempt to discover the molecular basis for the 

 reaction of cellular protoplasm to external stimulation has already produced the denatura- 

 tion theory of excitation and damage put forward by Nasonov & Aleksandrov. 



In conclusion, I should Uke to emphasize again that it seems to us that alteration in the 

 configuration of fibrillar protein complexes, i.e. alteration of the mechanochemical reac- 

 tivity of these polyelectrolyte systems, may be regarded as a primitive form of irritability, 

 that is to say, as the molecular basis for the evolution of the mechanisms whereby proto- 

 plasm reacts to stimuh from its environment. 



G. P. Kalina (U.S.S.R.): 



At present viruses are widely used as a subject for the study of hfe in its, morphologically 

 and biochemically, most primitive structures. The investigations of Fraenkel-Conrat and 

 Schramm, demonstrating the infectivity of the nucleic acid of tobacco mosaic virus when 

 freed from protein represent a scientific discovery of the greatest importance. I should 

 like to call attention to a subject for study which has been unjustly neglected, both in this 

 Symposium and in the latest edition of Acad. A. I. Oparin's book, which is very important 

 and may well be more satisfactory for the study of the problem in which we are interested, 

 namely the filterable forms of bacteria. The phenomenon of the formation, by bacteria, 

 of filterable forms has already been known for 50 years and is now generally accepted. 

 It may also be taken that the filterable forms are produced by the breakdown of bacterial 

 cells, most probably after impairment of the integrity of the bacterial cell, being similar 

 in nature to the protoplasts described by Weilbull, Stähelin, Oparin et al, McQuillen, 

 Salton, Lederberg and others. Filterable forms, however, can readily be differentiated 

 from protoplasts by virtue of their considerable stability in the external medium, the 

 fact that they can be conserved in the absence of a 'stabiHzer', and also by the relative 

 ease with which they can regenerate into cellular forms. We have shown that filterable 

 forms are to be found even in fresh cultures of bacteria which have not been exposed 

 to the action of mechanical, physical, chemical or biological factors. Of all the properties 

 of the filterable forms, the most noteworthy are their considerable stability in respect 

 of physical and chemical action, which exceeds the stability of the cellular forms, and 

 also their inability to multiply before they have turned into young cells. As Hauduroy 

 has shown, filterable forms may retain the potential ability to regenerate for many years 

 without any sign of metaboHsm. This anabiotic, 'Ufeless' condition changes under 

 favourable conditions, with the restoration of vital processes. When this occurs, the succes- 

 sive stages of regeneration of the bacterial culture from the filterable forms bears the un- 

 mistakable sign of ontogenic development, showing the essential stages of phylogenesis of 

 the species in question. Hence, one may put forward the hypothesis that the earUest stage 

 of this ontogenesis corresponds, to some degree, with the earliest stage of phylogenesis, 

 i.e. with the primitive coacervate state which, according to Oparin, was the first mani- 

 festation of hfe on the terrestrial globe. This also receives indirect confirmation from the 

 fact that the regeneration of bacterial cells from filterable forms can be hastened by in- 

 creasing concentrations of salt solutions which, it would seem, facilitate the coacervation 

 of the fine, filterable forms into the larger and more complicated molecules, which begin 

 to carry out independent metabohsm. 



In view of what has been said, I must beg all who are interested in the problem of the 

 origin of Ufe to use filterable forms, as being the most satisfactory models for the solution 

 of many of the partial questions associated with this problem. 



