MODIFICATION OF THE GERM-CELLS IN MAMMALS 125 



alcoholic lines. The pedigrees of a great majority of these 

 alcoholic animals could readily be given to cover several genera- 

 tions, but it does not seem advisable to enter into this detail, 

 since there is no possible chance that any differences which might 

 exist between the normal and alcoholic lines are due to different 

 degrees of inbreeding among the individuals of the two groups. 

 And further, in all the groups it is entirely out of the question 

 that any difference between the records of the control and the 

 records of the alcoholic may be due to the control having been 

 by chance originally good breeders and the alcoholics originally 

 bad. The control animals are in almost all cases either sisters, 

 brothers, parents or other blood relations of the treated animals. 



c. The number of animals alcoholized 



Recognizing the great variability in the breeding results from 

 the different individuals in a group of higher animals, such as 

 mammals, it has been deemed entirely essential to make our 

 experiment on a considerable number of males and females. 

 The mating records of two normal male guinea-pigs are fre- 

 quently quite different even though paired with the same fe- 

 males. It is also highly probable that different individuals will 

 differ in their susceptibilities and responses to the treatment, 

 so that the records of two or three males might easily prove con- 

 fusing even though all might exhibit some effects of the experi- 

 mental treatment. Thus the following twenty-eight males 

 have been treated with alcohol, and a number of matings from 

 each of these and their descendants have supplied the breeding 

 records. The first three are from the original 1910 stock Nos. 

 4 cf , 5 cf , and 6 cf , and the remaining twenty-five are animals 

 bred and reared in the colony or from the newly introduced 

 stocks: Nos. 43c?, 45 c^, 70 o^, 72 cf, 80 cf, 81 cf, 678 cf, 887 cf, 



AN 

 913 cf, Y~ 129 cf, 157 cf, 168 cf, 183 cf, 302 cf, 353 cf, 365 cf, 



AN 



574 cf ^493 cf,^^^^^^^ 771 cf,^^' 889 cf, 1091 cf, 1134 0^, 

 A A — - — 



A 



1153 cf, 1326 cf and 1327 cf. 



