No. 609] SHORTER ARTICLES AND DISCUSSION 569 



Two methods of inducing germinal variation seem practical. 

 The first is the treatment of the germ cells. MacDougal's 

 ovarial injections lie in this class. Tlie otlier method is to attack 



we may have reason to expect that the cells of the growing points 

 are probably in contact with the solution or some derivative of it. 

 If the chromosomes of a growing point can be influenced it is pos- 



