332 Action of the Genetic Material 



possibly too pessimistic for the future), might be used as a stimulating 

 cold shower for all of us, who talk more ghbly than clearly about 

 enzyme systems and their connection with genie action. There is 

 some reason why many biochemists laugh at what geneticists and 

 embryologists consider to be biochemical explanations. It is rather in- 

 teresting that the above-quoted biochemical embryologist, after hav- 

 ing expressed his views, continues in his search for the biochemical 

 control of embryonic segregation and ends up with a refuge in the 

 unknown, just as the embryologist did, when he states: "It may even 

 be that solutions of the true morphogenetic problems are beyond the 

 reach of enzymes. After all, the enzyme-substrate specificity seems 

 rather crude compared with the degree of specificity involved in dif- 

 ferentiation processes. Enzymes can be tools, but scarcely true causa- 

 tive agents in morphogenesis. And I think it is very significant that the 

 substances which in recent years have come into the center of bio- 

 chemical interest, the nucleoproteids, seem to offer especially wide 

 possibiHties with regard to specificity of action. Their connection with 

 the mechanism of gene action, and especially the intensely interesting 

 problem of plasmagenes, offer at present, the most promising approach 

 to the study of morphogenesis." Thus we face the distressing situation 

 that the geneticist expects the solution of his problem from the bio- 

 chemist, while the biochemist takes refuge in more or less vague 

 concepts of the geneticist. 



Hence, the geneticist is left where he was, as all our former 

 discussions bear out. We take it for granted that the nucleoproteins are 

 the master substances in genie action whether they act in the chromo- 

 somal, the intranuclear, or the cytoplasmic locality. We saw that none 

 of the real problems of morphogenetic segregation are solved by call- 

 ing those nucleoproteins within the cytoplasm plasmagenes. Actually, 

 we found that such a terminology is dangerous because it suggests a 

 solution which is no solution. The difficulty of the problem cannot be 

 better illustrated than by the fact that the biochemist gives up and 

 takes refuge in the unknown, the plasmagenes. 



It is certainly of interest to see that a geneticist with a consider- 

 able inclination toward thinking in terms of plasmagenes, Ephrussi, 

 concludes a brief discussion of the problem (which I have just tried 

 to analyze in more detail ) with a statement ( 1953 ) that I quote here 

 without endorsing all of it: "After a century of amazing progress in 

 the analysis of the cell and its genetic structure, we just return to the 

 notion of the cell as the ultimate unit of life, lost in the course of our 



