FAMILY HISTORIES 



51 



made a quick time record of 15 seconds. The records for this branch 

 of the strain are given in Fig. 13. As in the other branch we have 

 just discussed, No. 91 again produced an exceptionally quick and 

 uniform family in the sixth generation. This litter was composed of 

 three males and three females, Nos. 122 to 127 inclusive. Four in 

 the litter made time averages of fifteen seconds or lower, while the 

 other two took 32 and 33 seconds each. Their family average 

 amounted to 19.1 P.E. 3.4 seconds. No. 125, with an average of 9 



>(0/57w No'58w Nc>.y?w No'Ww No)55w Nol5/w NO/5SW No;53WNo/5y 



FIG. 13. Continuation of the White Family, No. 91 mated with No. 86. 



seconds, and No. 127, whose average was 15 seconds, were mated and 

 they produced in the seventh generation two litters. The first was 

 composed of six mice, Nos. 155 to 160 inclusive ; two were males and 

 four females. All these mice made averages slower than any of their 

 sixth generation kin. One male made an average of 62 seconds, two 

 females gave average records of about 90 seconds, one of 44 seconds 

 and another of 49 seconds. The family average here was fairly high, 

 amounting to 66.4 P.E. 7.6 seconds. The second litter was com- 

 posed of two males and three females, but Nos. 172 and 173 died be- 



