RESULTS. 



23 



No parent is a strict mulatto, hence the proportions of o : i : 3 : 3 : i 

 may be expected, approximately. The formula 0:2.5:7.5:7.5:2.5 

 does, indeed, approximate to the result obtained. 



Table 21. — Expectation is that the darker parent forms germ-cells 

 with I factor and with 2 factors for black, while the lighter parent 

 forms germ-cells with i factor and o factor. Hence the classes i, 2, 

 or 3 factors should appear among the children in the proportions 

 I, 2, I, or expectation for the nine progeny is o: 2.25 : 4.5 : 2.25 : o, not 

 very far from realization. 



Table 22. — This is the reciprocal of table 20. Expectation, cal- 

 culated in the same way as for table 20, is 0:0.6: 1.8: 1.8:0.6. The 

 result contains too few individuals to warrant speaking of an agree- 

 ment. 



Table 2j. — Both parents form gametes with either i or 2 factors; 

 consequently the zygotes will have 2, 3, or 4 factors in the proportions 

 of 1:2:1 or expectation is 0:0:4. 5:9:4. 5, fairly close to realization; 

 the shortage of the deeper-colored grades is probably due to the fact 

 that all fraternities include young children whose pigmentation is not 

 fully developed. 



Table 24. — The father's gametes all have 2 factors; the mother's 

 either i or none ; consequently there may be expected an equal number 

 of children with 3 and 2 factors, but the number of children is too 

 small to test the hypothesis. 



We may now set side by side expectation and realization in all 

 the foregoing tables and compare the sums, so as to get larger numbers 

 with which to test the hypothesis (table 25). 



Table 25. — Comparisons of realization and expectation in 631 offspring. 



In comparing realization with expectation, we see that there is an 

 actual deficiency in the o-factor class and a corresponding excess in 

 the i-factor class, which leads us to conclude that it would have been 



