22 HEREDITY OF SKIN COLOR IN NEGRO-WHITE CROSSES. 



black may be of the same type (i.e., either A or B), and then 50 per 

 cent of the offspring will have 1 factor for black and 50 per cent will 

 have 2 factors. In table 15 none of the 2 -factor parents are mulattoes, 

 and the offspring fall into only two categories ; and they approach the 

 expectation on the second hypothesis, viz., an equal proportion of 

 individuals with 1 factor and 2 factors for N. 



Table 16. Since the 1 -factor parent carries germ-cells with no 

 factor or with 1 factor, offspring are of two sorts, in equal proportions, 

 with 2 factors or 3 factors for black. This expectation is, it must be 

 confessed, not satisfactorily met; but not much weight can be given 

 to this result, as only two fraternities are involved. If we unite this 

 table with the reciprocal of table 24 we get a distribution 0:0:5:8:1, 

 which is close to the expected 0:0:7:7:0. The one individual that 

 falls in the 4-factor class (with N 57) is close to the lower limit of that 

 class (N 55), and may be considered an extreme variant of the 3 -factor 

 class. 



Table 17. Expectation here is the same as in the case of table 10. 

 The three expected classes, and only they, appear. There is, however, 

 an excess of the lightest grade among the offspring that inevitably 

 leads one to suspect that the actual father was in some cases lighter 

 than the putative father, a result rendered the more probable from the 

 desire of light mothers to have white children. 



Table 18. This is the reciprocal of table 15. Of the 2 -factor 

 fathers only one is a strict mulatto (B. 20). By such a father four 

 possible classes of children might arise, but this possibility is not realized 

 in these six children. For the rest, expectation is that the two classes 

 of 1 factor and 2 factors for N shall appear in equal frequency, although 

 the possibility of unions giving offspring with o factor and 3 factors 

 is not excluded. Actually here, as in table 15, the two classes (1 factor, 

 2 factors) are realized and they only, and the frequency is approxi- 

 mately equal. 



Table 19. This is the most complex of all the matings and yields 

 the greatest variety of offspring. In three cases, at least (marked b), 

 both parents are known to be strict (Fi) mulattoes, and they are prob- 

 ably so in others. Two mulatto parents should yield offspring belong- 

 ing to all five classes and in the proportion of 1 : 4 : 6 : 4 : 1. Two- 

 factor parents who are not Fi mulattoes may be expected to give 1-, 

 2-, and 3 -factor offspring only, so in this case the proportions of the 

 five classes will be o : 1 : 2 : 1 : o. It is impossible to say, in all cases, from 

 which of the given parents the one formula is to be expected and from 

 which the other. If we assume that half of the matings are of each 

 kind expectation will be 2.8: 22: 38.5: 22: 2.8. This is fairly close to 

 the proportions actually obtained. 



Table 20. Expectation is here either that the offspring shall fall 

 into two classes (if the father is a strict mulatto) or into four classes. 



