INHERITANCE OF MINOR VARIATIONS IN INTENSITY. 



91 



yellow 4 and cream 7 , mean at cream 5 .i very distinctly paler. Litters 

 which should give both have given the entire range with two modes, 

 at yellow 3 and cream 5 , respectively. It is especially to be noted that 

 among 13 of these, which were given grades before their constitution 

 was known, 4 ranging from yellow 2 to yellow 4 proved to be homozygotes, 

 while 9 ranging from cream 5 to cream 7 proved to be heterozygotes. 

 Dilutes known to transmit red-eye (C d C r ) have been either yellow 4 or 

 cream 5 , mean at yellow 43 . These should be compared with those of 



Table 40. — Effect of age on intensity of black. 



the same stock (S. Am.) which transmit albinism. The difference, 

 yellow 4 . 3 compared with yellow 46 , is too small to be relied on. Litters 

 which should give both C d C r and C d C a have given a range of yellow 4 to 

 cream 6 , as expected. Thus grade yellow 4 may be any sort of a dilute; 

 one more intense is quite certain to be homozygous (C d C d ) ; one more 

 dilute is quite certain to transmit either red-eye or albinism. 



The influence of stock can only be recognized surely in the case of 

 those known to be C d C a . The numbers are too small among the 

 homozygotes. Among the heterozygotes (C d C a ) it is clear that those of 

 dilute and miscellaneous stocks, both with a mean of cream 5 . 5 , are 

 distinctly paler than those with an admixture of BW or S.Am, blood 

 with means from cream^ to creamy. 



The data in table 39 indicate that yellow undergoes no appreciable 

 change in intensity during the life of an animal, except in the dilute 

 selection stock. In this case there is a change from cream 5 . 2 at birth 

 to creamg.o when adult, among those carrying albinism. 



