(ii) the modus operandi inconceivable 28 



inconceiyable, we decline to believe that they 

 are more than appearances. This is their 

 second argument. But as the " impassioned 

 controversy," as Delage calls it, has gone on, 

 this argument, it is hardly unfair to say, has 

 changed its form. No process of transmis- 

 sion being conceivable, it is assumed that no 

 such process is possible. In this way the 

 Neo-Darwinians relieve themselves of the 

 difficulty there is on their side of proving a 

 negative. But assumption is not argument, 

 and our mere ignorance of the " how " alone 

 will not justify us in rejecting prima facie 

 evidence. We do not brush aside the facts 

 of gravitation because we are utterly ignorant 

 of the process which they involve. 



We certainly are entirely in the dark 

 as to how structural changes in the body 

 of the parent can aflfect at all the structure 

 of the germ which it nourishes; since the 



