MODIFICATIONS OF THE GERM-CELLS IN MAMMALS 211 



in former papers though analyzed in further detail. They are 

 also very similar to those recorded by Pearl ('17) in his table 14. 

 From a physiological standpoint it seems to us that these quali- 

 ties are all closely associated and finally come down to the three 

 related qualities: ability to develop normallj^, grow rapidl}^, and 

 live to maturity. An animal possessing such qualities is usually 

 termed a vigorous individual. At present it can only be stated 

 that these properties are due to the vigor of the germ cells from 

 which the individual arose. The qualities discussed might all 

 involve a limited range of physiological factors so far as present 

 knowledge permits a separation of such factors and they only show 

 on the part of the alcoholics a reduced capacity of development 

 and growth. The same underlying cause may actually account 

 for the abnormal sex-ratios, as has been pointed out in an 

 earlier section. 



Leaving the environment out of account, the normal develop- 

 ment, growth and length of life of a zygote varies with the 

 perfection or vigor of the germ cells from which it originated. 

 An experimental treatment may act upon the germ cells of an 

 animal so as to modify them in some general way which lowers 

 their ability to react normally in combination with germ cells 

 from another individual. Thus zygotes are produced which 

 tend to develop abnormally, grow slowly, or die during early 

 stages of their existence, depending upon the degree of modifi- 

 cation the treated germ cells have suffered. We are fully em- 

 barrassed by the unsatisfactory nature of such statements, but 

 have been unable to gather scientific facts that would permit 

 any more definite estimate of the situation. 



All of our experiments on the modification of the germ cells 

 have given results which express themselves in some such general 

 fashion. Yet the germ plasm has been definitely modified and 

 the subnormal condition is transmitted through a number of 

 generations beyond the animals directly treated. This result is 

 original on the complex material used, and is of primary impor- 

 tance, although it may be disappointing in that it has not shown 

 a modification in the mode of behavior of some particular char- 

 acter known for its ^lendelian inheritance. 



