EVIDENCE FROM EXPERIMENT 165 



that in those experiments the behavior of the first 

 generation is difficult of interpretation. In these 

 experiments the male cells and the female cells, and 

 sometimes both, have been subjected to conditions 

 of experiment at a susceptible stage. 



11 Morgan has raised the question, why do indi- 

 viduals, developed from eggs which have been sub- 

 jected to conditions of experiment and fertilized 

 with normal sperm, not give a subsequent hybrid 

 behavior? No hybrid splitting has ever been found 

 in any of my experiments, or in those of MacDougal 

 or Gager. The resulting modification reproduces 

 itself true to type, and does not give subsequent 

 splittings suggestive of the combination of different 

 factors or unit-characters. If there are unit-char- 

 acters, it is logical to expect that in experiments of 

 this kind the experiment would modify the unit- 

 character in the germ-plasm, and that this modified 

 unit-character would then behave, when crossed 

 with its normal homologue, exactly as hybrids do in 

 other cultures. The total lack of this behavior in 

 my experiments, and those of MacDougal, Gager, 

 and others, might be considered good evidence that 

 there are no such things as unit -characters, nor in 

 the germ cells any potentiality capable of individual 

 removal or behavior. Any such deduction, however, 

 is unwarranted and contrary to known facts, and, 

 furthermore, these modified characters themselves 

 show that after establishment [italics mine] they are 

 alternative and capable in many instances of re- 



