THE UNDERLYING IDEA StI 
needed to unfold itself, or that the hen’s egg had 
within it a miniature chick which only needed the 
warming process in order to make it evident, could 
not possibly survive the invention of the microscope. 
We may not, and we certainly do not, know everything 
that is in one of these eggs, but we do know most 
certainly that what is there has no resemblance to 
what it will be in time. The biologist finds in the 
nucleus or central core of every growing and repro- 
ducing cell certain minute bodies which Weismann be- 
lieves do much to determine the growth of the rest 
of the cell. He believes also that there are many 
more such “determinants” than are necessary for the 
reproduction of the cell. Each of these determinants 
may be fitted to produce slightly different results, but 
what decides which of them shall have its own way is 
quite uncertain. It may be that one determinant hap- 
pens to be more favorably placed than others in the 
cell and that it has consequently secured more of the 
nourishment that comes to the cell in the blood of its 
parent. If this is true it would certainly be favored 
in the competition. We are becoming quite certain 
that whatever variations arise really start in the egg. 
The simplest conception as to the cause of variation 
would seem to be varied experience. One man trains 
his brain, another his hand; and in each case the organ 
so trained develops. But science is strongly of the 
