The Sex-Ratio in Human Populations 
is little doubt, however, in my mind, that an intensive drive, if 
it were thought desirable, would produce this result in a short 
time. 
There is one final point here which is of some importance, I 
think, in connexion with our present discussions ; so far as 
work on animals is concerned, exposure to and preservation at 
low temperatures may or may not kill any particular sperma- 
tozoon, but it does not damage the genetic properties of those 
still able to effect fertilization. It seems that the damage caused 
to spermatozoa by low temperatures, which can be overcome to 
varying degrees by special methods, is first to their vegetative 
functions, rather than their genetic material, so that if a sper- 
matozoon preserved at low temperature 1s able to effect fertiliza- 
tion, it will, according to experience with animals, produce 
normal young. 
By contrast with the male gamete, the preservation of ova, 
whether fertilized or not, has hardly been investigated as yet, 
and so far, even in mammals, I do not think that either ferti- 
lized or unfertilized eggs have been preserved for any significant 
length of time. Moreover, techniques are much complicated by 
the fact that as yet, even in experimental mammals, ova can be 
obtained only by means of surgery, and the same applies of 
course to the transference of eggs or their return after in vitro 
treatment. However, all these problems will be solved one day 
or other, and the transference of fertilized eggs of the required 
sex will be possible in man in the course of time. 
Among the many sociological queries arising from such 
prospects is this: if the sex of the projected child could be 
chosen by the parent, which sex would be chosen more fre- 
quently? With the present social set-up, it is doubtful whether 
the overall ratio would be much affected, as witness the com- 
mon anxiety to have a family nicely balanced between boys and 
girls. In fact, we may conclude that even if and when sex 
predetermination becomes possible, so far as the sex-ratio is 
concerned the future of man will be about the same as his past. 
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