24 Outline of Genetics 



character as coat color might not respond to artificial 

 manipulation of the germ cells, it is still possible that 

 there are other characters, more fundamentally tied up 

 with the metabolism of the organism, that could be 

 affected by such treatment. 



Numerous experiments confirmed these findings of 

 Castle's, but there was one field of investigation from 

 which rather contradictory results began to be accumu- 

 lated. The numerous studies that have been made dur- 

 ing the last few years on inheritance in the microorgan- 

 isms have been ably summarized by Jennings (13). 

 Here there appear some striking indications of inheritance 

 of acquired characters. 



''The germinal or genotypic constitution in most 

 organisms is extremely stable; in many stocks it changes 

 not at all, so far as observation goes. To alter it by 

 physical or chemical agents is usually to kill it. In 

 some of the lowest organisms — rhizopods, bacteria, some 

 infusoria^ — it changes with somewhat greater frequency, 

 though still rarely. The nature of the changes, and 

 whether they may be permanent, or must after genera- 

 tions revert to the original condition, is in some dispute. 

 In these same organisms, environmental agents may pro- 

 duce changes persisting through many generations of 

 uniparental reproduction and even through biparental 

 reproduction, the period of persistence depending partly 

 on the number of generations through w^hich the pro- 

 ducing agent acted. This suggests that inherited char- 

 acters as permanent as any that exist might in time be 

 so produced. In spite of important differences of opinion 

 among investigators, to the reviewer the facts in uni- 

 parental reproduction seem to point more toward the 



pfOfOnT LBRARf 



N. C. Stale College 



