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THE AMERICAN NATURALIST [Vol. L 



been no change in the tendency to produce offspring of 

 a certain sex, since the remaining testis originally pos- 

 sessed an advantage. 



Finally, then, from the above experiments there is no 

 question that the material basis of the hereditary quali- 

 ties has been injured, since alcoholized males have trans- 

 mitted the injury to four generations during a period of 

 almost five years. In other words, as stated above, chro- 

 matin injured five years ago is now living in the great- 

 grandchildren of the individuals in which it was injured. 



Bardeen with the X-ray and Oscar Hertwig with ra- 

 dium have induced similar injuries by directly treating 

 the spermatozoa, but these cells were so greatly injured 

 that only the immediate effect upon the developing em- 

 bryo was shown. The present experiments, however, 

 demonstrate the passage or transmission of the injured 

 chromatin from generation to generation during a period 

 of years. The behavior of the carriers of heredity be- 

 comes pathological just as any other organ with a normal 

 function may behave in an abnormal or pathological 

 manner. 



Mammals are particularly adapted to the study of such 

 features of heredity as this, on account of their typical 

 structure and large, easily observed organs. The com- 

 plexity of their structure and behavior further permit the 

 possibility of slight modifications becoming visible 

 through abnormal conditions of their nervous system, etc. 

 Thus with such material as guinea pigs a few experiments 

 of this kind may furnish certain clues to the processes of 

 behavior of the chromosomes that less plastic and simpler 

 forms might never present in such a manner as would be 

 recognizable. 



On the other hand, the small litters and comparatively 

 slow breeding render these higher animals unsuitable for 

 an exhaustive analysis of many of the intricate problems 

 of normal heredity. 



