6o 



Heredity and Eugenics 



new stock was at any <Uher time introduced in either series, 

 the two remaining distinct at all times excei)t in the second 

 generation. It will be observed that a change m the aver- 

 age grade of the parents is attended by a corresponding 

 change in the a\-erage of the offspring, and likewise in the 

 range of ^'ariation in the offspring. The amount of varia- 

 bility of the offspring is not materially affected b}' the 

 selection, but the average about which variation occurs is 

 steadily changed, as are also the limits of the range of 

 variation. 



TABLE I 



Results of Sele(;tii)x for JIodification of the Color-Pattekn of 

 Hooded Rats 



Average Grade i Average Grade 

 Parents ' Offspring 



Number of 

 Offspring 



Plus series i . 



3- 



4- 

 5 ■ 

 6. 



7- 



■50 

 ■51 

 -73 

 .09 



■33 



■SI 

 53 

 ■65 



Total , 



Minus series i . 

 2. 

 3- 

 4- 

 5- 

 6. 



7- 

 8. 



I -46 

 1. 41 

 I 56 

 1 .09 



1-73 



1 86 



2 .00 

 ^-°3 



Total . 



2 05 

 1.92 

 ^-51 



2 90 



3 00 

 3-14 

 3-30 



150 

 471 

 341 

 444 

 610 



834 



874 



91 



I 00 

 1.07 

 I. 18 

 1.28 

 1. 41 



I -56 

 I . 70 

 1.78 



3,SiS 



SS 

 132 

 195 

 3 -"9 

 701 

 1,252 

 1,544 

 713 



4,921 



The interesting feature of this experiment is the pro- 

 duction, as a result of selection, of wholly new grades, in 

 the narrow series of animals having less pigment than any 

 known type other than the albino; in the wide series, of 



