82 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



left unmarked, so that the former stood for gametes having the character 

 pigmentation, and the latter for gametes having the character albinism. 

 The contents of each bag, when thoroughly mixed, were supposed to 

 represent an indefinite number of the two sorts of gametes produced in 

 equal proportions by a heterozygote. If, now, a single beau be taken at 

 random from each bag, three combinations are possible : (1) both beans 

 may be spotted, representing a pure D individual ; (2) one may be 

 spotted, the others unspotted, I'epresenting a heterozygous, D(R), indi- 

 vidual ; or (3) both beans may be unmarked, representing an albino, R. 

 For comparison the same number of drawings was made as there are in- 

 dividuals represented in Table G (page 84) of the progeny of heterozy- 

 gotes from spotted and albino parents. The total number of these young 

 was 214, of which 159 were pigmented and 55 were albinos, so that the 

 two classes are practically as 3 : 1. Three series of drawings were made. 

 In the first and second of these, the number' of beans in each bag was 

 indefinite, but in the third series, the beans representing the gametes of 

 the female parent were made only twice as many as the number of young 

 actually occurring in any given litter of the table and, of course, repre- 

 sented equal numbers of the two sorts in each case. The totals for each 

 of the three series of drawings agreed very closely with the numbers 

 actually obtained with the mice, the agreement being almost perfect in 

 the case of the third drawing, in which the conditions of the experiment 

 were made to correspond most closely with those in the mice. In a 

 small number of consecutive drawings there was sometimes a consider- 

 able excess of one class or another over its expected ratio, but these 

 discrepancies tended to balance one another in the long run, just as 

 observed with the mice. Table E gives a summary of these results. 



TABLE E. 



Result with the mice (Table G) 



First drawing, number of gametes indefinite 



Second " " 



Third drawing, gametes of female double the 

 number of ofTspring 



Expectation 



Pigmented, 

 D D(Il) 



159 

 59 + 110 = 1G9 

 48 +113 = 161 



53 + 107 = 160 

 53.5 + 107 = IC0.5 



Albiuo, 

 R 



00 



45 

 53 



54 



