362 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1957 



taught that the essence of a thing is not what it is, but what it does, 

 and the doing of something involves time ; hence there may be good 

 reason always to consider the virus with time. Regardless of certain 

 mental restrictions that may differ from person to person, I think 

 there is no escape from the acceptance ultimately of viruses, including 

 the crystallizable viral nucleoprotein molecules, as living agents. 

 This must be done because of their ability to reproduce or to bring 

 about their own replication. Certainly the essence of life is the 

 ability to reproduce, to create a specific order out of disorder by the 

 repetitive formation with time of a specific predetermined pattern 

 and this the viral nucleoprotein molecules can do. 



Of course, it would have been dull indeed if the first formed living 

 agent had been restricted to exact duplicates of itself. The logical 

 reasoning provided in schemes such as those outlined by Calvin, 

 Haldane, Horowitz, Oparin, and Urey by means of which relatively 

 complex organic substances could have arisen from inorganic matter 

 provides justification for assuming that a chemical structure, per- 

 haps something like nucleic acid, which possessed the ability to repli- 

 cate, did come into being once upon a time. It need to have happened 

 only once, and thereafter without the great phenomenon of mutation 

 it merely would have kept going until it had filled the world with 

 replicates of this precise structure or until it had exhausted the start- 

 ing materials. However, Nature has provided a built-in error so 

 that the replication process is not perfect and about one in every mil- 

 lion or so replicates is slightly different. This change, which has been 

 of tremendous fundamental importance, we now recognize as muta- 

 tion, and as these errors or differences were accumulated by replicat- 

 ing structures it became necessary to make formal recognition of them. 

 These differences or markers we now call genes. We do not recognize 

 genes directly but only by differences. Needless to say, some physical 

 structure had to be responsible for the accumulation, preservation, 

 and potential exhibition of these differences and this assembly of genes 

 we call a chromosome. The incorporation of one or more assemblies 

 of genes into a structure possessing a limiting membrane, which we 

 now call a cell, then made possible gene interchanges between these 

 cellular assemblies. This genetic interchange by the fusion of two 

 cells, a sexual process, also represents a phenomenon of the greatest 

 fundamental importance for this permitted genetic recombination, 

 a factor that has served to speed up the evolutionary process im- 

 measurably. Therefore, life as we know it today is dependent not 

 only upon reproduction but also upon mutation and genetic 

 recombination. 



Now let us consider for a moment the relationships between genes 

 and viruses since we see that both are related to life. Muller's esti- 



