DISCUSSION 
potent and sterile. I think more research is needed on the 
problem of sterility in the male. 
If we ever adopt Muller’s techniques, we shall have to have 
biographies, not only of the great man whom we are considering 
as a sperm donor, but also of his antecedents. However, the 
present state of our knowledge of human inheritance is ex- 
tremely fragile. I think we are still at the beginning of the 
study of human heredity, and before applying it I feel we must 
know it much better. 
May I finish with a story by the German biologist, von 
Uexkiill, about a man who discovered his own shadow. This 
man came to believe that his shadow was a living thing. At 
first he imagined his shadow to be his servant, because it 
copied all his movements; but he gradually began to doubt this 
and to believe that he was imitating the shadow. Thereafter he 
showed more and more consideration for his shadow, allowing 
it to have his seat or bed while he himself remained uncom- 
fortably to one side. ‘This man was eventually reduced to being 
the shadow of his shadow. Perhaps we also are too conscious 
of our shadows and forget what we are ourselves. 
Lederberg: In answer to Dr. Bronowski’s question about our 
motivation, I think that most of us here believe that the present 
population of the world is not intelligent enough to keep itself 
from being blown up, and we would like to make some provision 
for the future so that it will have a slightly better chance of 
avoiding this particular contingency. I am not saying that our 
measures will be effective, but I think this is our motivation; 
it is not the negative but the positive aspects of genetic control 
that we are dealing with here. 
On the other hand I have serious doubts about the proposals 
for controlling reproduction that have been presented to us. 
The aspects of social control that seem to be necessary to make 
these proposals technically effective are I think extremely 
offensive and extremely dangerous, certainly in our present 
social context. But leaving the matter to individual choice, 
which from a social standpoint is the most ideal, is certainly not 
going to be technically effective. And if people are allowed to 
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