THE UNDERLYING IDEA . 5 1 



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 microscopCo 

 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 



