ALLEN. THE HEHEDITY OF COAT COLOR IN MICE 



103 



111 a total of 273 rats, it is expected tliat 17i\; will be albinos, and 

 there are actually 18. It is evident that albinos can result from any one 

 of three matiiigs, DRR X DR-R, D R x DR, or DRR x DR. and 

 in each case the albinos are to the pigmented rats as 1 : .3. In ca.ses 7, 

 y, 12, 13, and 15 this ratio obtained, but in cases 8 and 11 the albiiio.s 

 are more nearly as 1 : 16, and it is not improbable that the totals in the 

 two latter cases rej)resent the results obtained where entire families con- 

 taining two sorts of heterozygutes were bred i)iter se. 



Table N is reproduced from the data given by Crampe ('85) on 

 page 004. 



TABLE N. 

 (Based on observations of Crampe.) 



This lot gives a total of 166 young, and 9 are albinos where 10| are 

 expected. If the matings represented by this table are those given under 

 our "Case II," we expect that ^g^ or 31 of the animals produced will be 

 unspotted (i. e. of classes D and D-R), and there are actually 27 en- 

 tirely black. It is' impossible to say which of the remaining individuals 

 belong to the DR, D-DR, or DR-R classes, since these combinations 

 may give a varying amount of spottedness. 



The last of Crampe's ('85) tables to be considered (Table 0) is that 

 given by him on page 612, which contains the totals obtained by inbreed- 

 ing, for five generations, families of gray-white rats among which were 



