Influence of Environment 247 



when brought back to normal conditions the first generation was 

 weak but the second was normal. On -the other hand Stockard 

 finds that the injurious effects of alcohol on guinea pigs persist 

 through two or more generations. In man alcohol may have an 

 "induction" effect on offspring, but fortunately it does not seem 

 to alter hereditary constitution. Probably of a similar character 

 are Stunner's results ; he found that mice raised in the cold have 

 shorter tails than those raised at higher temperatures and this 

 modified character appears in the next generation. If this is an 

 after-effect or ''induction" it should disappear in the following 

 generations. 



Kammerer found that salamanders with black and yellow spots 

 when reared on yellow soil gradually ^lose their black color becom- 

 ing more yellow, and their young continue to grow more yellow 

 until finally almost all black may disappear. The offspring of 

 such salamanders are said to be more yellow than normal; but 

 this work has been called in question and needs confirmation. 

 Even if confirmed the result may be an after-effect or "induction" 

 which would soon disappear under usual conditions, and as yet 

 there is no conclusive evidence that it is really inherited. 



Probably such cases are not instances of true inheritance ; they 

 do not signify a change in the hereditary constitution but an influ- 

 ence on the germ cells of a nutritive or chemical sort comparable 

 with what takes place when fat stains are fed to animals ; the eggs 

 of such animals are stained and the young which develop from 

 such eggs are also stained, though the germinal constitution re- 

 mains unchanged. The very fact that the changed condition is 

 reversible and that it disappears within a short time is evidence 

 that it is not really inherited. 



One of the most interesting and convincing cases of the inheri- 

 tance of an experimentally induced character has been reported by 

 Guyer and Smith* with respect to certain eye defects in rabbits. 



* Guyer, M. F., and Smith, E. A. Studies on Cytolysins. II. Trans- 

 missions of Induced Eye Defects. Jour. Exp. Zool. 31, Aug. 1920. 



