EXPERIMENTAL. 



33 



STATISTICAL TREATMENT. 

 COEFFICIENTS OF VARIABILITY LITTER BY LITTER. 



Coefficients of variability were calculated for each measurement in 

 nearly all litters. (See table 4.) Being based en small numbers of obser- 

 vations, these coefficients show no uniformity, but they indicate that the 

 different parts measured vary to some extent independently of each other. 

 In some measurements a greater variability is found in a back-cross litter 

 than in the FI generation in the same family, whereas in other measure- 

 ments from the same sets of animals the FI generation may show greater 

 variability; for instance, in family 647 the coefficient of variability for 



TABLE 4. Coefficients of variability of the several litters of rabbits studied, in each 



of the seventeen measurements taken. 



P. O. in generation FI is 5.1, while in the back-cross litters it is 3.8, 2.7, 

 and 3.4; in the same family the coefficients of variability for Te. are: 

 FI = 1 .3, back-cross = 3.5, 3.6, and 2.8. Similarly the measurements Na. 

 and H. show coefficients for FI larger than any for the back-crosses, and 

 Za., N., M., U., F., T. have coefficients of variability for F x smaller than 

 any for the back-crosses. The coefficients of FI for the other ten meas- 

 urements are within the range of the back-cross coefficients. The other 

 families all show similar irregularities. 



