ACQUIRED CHARACTERS 163 



contained eggs. In a word, the egg produces the 

 body — not the body the egg. 



All this is now conceded by everj^one familiar with 

 the evidence ; but two further points are open to dis- 

 cussion. The first of these involves the possibility 

 that the germ-cells may be affected by the vicissi- 

 tudes of the body-cells, so that when their turn comes 

 to produce a new individual they reflect in some way 

 the changes that have been impressed on the body- 

 cells. If this takes place, the inheritance of acquired 

 characters would not be incompatible with the cell 

 theory although extraneous to the theory. The sec- 

 ond point relates to the possibility that the changes 

 in the external world that affect the body may pro- 

 duce a corresponding change in the germ-cells. No 

 amount of argument or a priori reasoning is likely 

 to settle these problems ; but fortunately there is at 

 the present time a large body of evidence, and some 

 of it experimental evidence, that is significant, and, 

 I think, convincing. Here, if anywhere, we may hope 

 to find proof on which to base a reasonable judgment 

 of the situation. To this evidence, then, I propose to 

 appeal. 



The evidence is of various sorts, and mav be 

 roughly grouped under several headings. First, that 

 of the supposed inheritance of use and disuse. This 

 takes us back to Lamarck, but while he rested his 

 case on generalities that were often fantastic, such as 

 the origin of the giraffe's long neck, there is now a 



