24 



BULLETIN 1121, U. S. DEPARTMENT OF AGRICULTURE. 



ADULT WEIGHT. 



The complete growth curve has been studied in those animals which 

 have been saved beyond 33 days. The details will not be discussed 

 in the present paper. It may be said, however, that a pronounced 

 effect of crossbreeding is observable in the fu'st generation of crossing 

 and that about half of the uicrease is lost in the first generation of 

 renewed inbreeding. 



Table 8 shows the average weights of males and females in the five 

 large inbred families and in the random-bred stock, 1916 to 1919 

 inclusive, taken at the time of recording a litter at the ages of 12 or 13 

 months. The females are thus not pregnant. 



Table 8. — Average weights at 12 or 13 months (1916-1919); taken after birth of litter, 

 inbreeding experiments and random-bred stocks. 





I 



lales. t Females. 





J 



Family. 



Num- 

 ber. 



Weight 

 (grams). 



Num- Weight 

 ber. (grams). 



2 



36 

 31 

 20 

 32 

 16 



716± 6.9 

 845± 9.2 

 700 ±10.1 

 770±10.4 

 757±17.0 



35 625± 5.3 



13 



33 1 686±11. t 



32 



21 ' 649± 7.8 



35 



32 669 ± 8.6 



39 



14 653±19. 1 







Total inbred 



135 



58 



761 ± 5.4 



852± 9.9 



135 i 657± 4.5 



B 



60 700± 7.9 







The superiority of the males over the females, of the crossbreds 

 over the inbreds, and the differentiation among the inbred families, 

 are brought out. 



In Table 9 animals from the first cross between inbred families, 

 and from the first generation of renewed inbreeding, are compared 

 with the inbreds used in crossbreeding experiments. As in Table 

 8, the weights were taken at 12 or 13 months of age after the birth 

 of a litter. These inbreds are not included in Table 8. 



Table 9. 



-Average weights at 12 or 13 months (1917-1920); taken after birth of litter. 

 Animals used in crossbreeding experiments. 



Experiment. 



Males. 



Num- 

 ber. 



Weight 

 (grams). 



Females. 



Num- 

 ber. 



Weight 

 (grams). 



Inbreds (in CO, AC, CA).. . . 

 CO (in CC, Cl, CA, AC) 

 Cl (inC2) 



776 ±6.4 

 865 ±8.8 

 824 ±13.2 



641 ± 4.8 

 726 ±6.6 

 667 ±17.5 



