No. 592] 



IXDIVIIX'AL DIFFERENCES 



235 



Another family, mostly yellow, was derived from a 

 yellow female and an unknown male, probably white. The 

 F 1 from this mating gave a litter of six, Nos. 32 to 37 in- 

 clusive. The records of 5 of these (one died) are given in 

 Table III and are graphically represented in Fig. 1). The 



only female of the litter (No. 37) mated but once, and it is 

 not known with which brother. She bore in the F 2 , two 

 females and a male (Nos. 54, 55, 56). Both females of 

 this generation were crossed with their brother and two 

 litters resulted. No. 55 X 56 gave Nos. 68, 69 and 70 in 

 the F 3 , and No. 55 X 54 gave Nos. 61 to 64 inclusive. 

 From a survey of the complete records of these mice, it 

 is seen that although the F 2 and F 3 generations came from 

 the female, No. 37 (which made the exceptionally low 

 record of 17), still two of her young in the F 2 made poor 

 records, and Nos. 61, 64 and 70 in the following genera- 

 tion did the same. 



The records of a family of white and colored mice are 

 given in Table IV and Fig. 10. The two parents and the 

 four offspring all have good records. It is to be regretted 

 that no further litters were obtained from this family. 



