STABILITY OF THE GENE 299 



reported the results are not like this, for a mouse with 

 abnormal brain and full-sized eyes may produce offspring 

 that have defective eyes. In other words, there is not here 

 a specific effect, but a general one. 



The other interpretation is that the germ-cells of the 

 young mouse in utero are affected by the radium. When, 

 in turn, these germ-cells produce a new generation, the 

 individuals are defective because the same organs whose 

 normal development was most disturbed are the organs 

 that are most easily affected by any alteration in the 

 course of development. They are, in a word, the weakest 

 or most delicately balanced phases of development, and 

 therefore the first ones to show the effect of any depar- 

 ture from the normal course of events. This is, I think, 

 at present the most plausible explanation of these and 

 similar experiments. 



