740 



THE AMERICAN NATURALIST 



[Vol. L 



the exaggerated differences which seem to exist, the fol- 

 lowing discussion is offered. It is written with no wish 

 to codify or defend the opposing positions, but rather as 

 an attempt to formulate the issue a little more clearly by 

 presenting two views, which appear to have advocates, of 

 the nature of the changes in the germ plasm. 



The view to be called the "first" is as follows: The 

 changes in the germ plasm are in the nature of fluctua- 

 tions, now larger, now smaller, but continuously appear- 

 ing; they lead in all directions. This is true of all in- 

 heritance, whether or not it be factorial (Mendelian) in 

 basis. If it refers to Mendelian inheritance the potential 

 grade of the factor in question, as found in any zygote, 

 acts as a mode about which the fluctuations in potentiality 

 occurring in the next generation are grounded. In other 

 words, although a zygote may include the strongest po- 

 tential grade of a factor that has appeared, the inevitable 

 fluctuations in this factor that are found in the different 

 gametes formed by this zygote will include, together with 

 those like and weaker than the parent, some with stronger 

 potentialities than the parent. 



The view to be called the "second" is as follows: The 

 changes in the germ plasm are discontinuous; they ap- 

 pear fortuitously. They may strike out in almost any 

 direction, as a projectile may be aimed in "any direc- 

 tion," in contrast to the "all directions" taken by the 

 waves of sound when the projectile explodes. 



According to the first view, selection would result in 

 modification in any direction the breeder might desire, 

 irrespective of variational tendencies shown by the 

 animal. To maintain conformity to type would require 

 as constant selecting as would be required to obtain di- 

 vergence. According to the second view, selection could 

 progress only in certain directions, depending on how the 

 germ plasm happened to change ; the variational tenden- 

 cies of the animals would probably suggest these direc- 

 tions. Conformity to type would be considered to be a 

 fundamental phenomenon due to the conservative tend- 



