192 



E. C. MACDOWELL 



TABLE 4 



Coefficients of variability of weights, arranged by generations. Each fraternity is 

 considered separately in the hack cross (B.C.) 



these weights might bear little or no conviction, on account of 

 the roughness of their estimation, as cumulative evidence in 

 connection with the results based on bone measurements, they 

 certainly may be considered. 



CONCLUSION 



The conclusion to be drawn from these observations seems 

 clear. The back cross is more variable than the first filial gen- 

 eration. This appears in the relative distributions of the co- 

 efficients of size of the two generations, whether compared by 

 observation or by standard deviations : it is found when the two 

 generations are classified one character at a time, in relation to 

 the original parents, whether single families or whole genera- 

 tions are considered: and finally the coefficients of variability 

 of the estimated body weights support the same conclusion. 

 There occur characters among the back cross offspring that are 

 smaller than the corresponding characters in the small parent 

 and others that are larger than the modes of the first generation 

 large parents. 



