IN RATS AND GUINEA-PIGS. 



t3 



thcfi'i/ic/aafs 



50 

 1-0 



35 



30 



35. 



SO 



/S 



10 



t4.5 



24-. S 



345 



44.5 



54.5 



64.S 



74.S 



34.5 



Grade 4.5 



Fig. 3.— Variation in extent of the back-stripe in lots il to F of hooded rats, showing the effects of cross- 

 ' breeding with rats of Irish pattern. The positions of the means are shown by vertical lines. 



