No. 524] CHROMOSOMES AND HEREDITY 471 



tative relations are factors in heredity, and how far the 

 chromosomes support such an interpretation. If, as we 

 have seen, the development of a character depends on 

 the amount of a given material rather than on its pres- 

 ence or total absence as the theory of pure gametes de- 

 mands, may not this view give an interpretation of the 

 role of the chromosomes in inheritance? 



Let us see where such an interpretation leads. By 

 means of diagram A, I have tried to indicate one way 

 in which a quantitative interpretation of the facts of 

 Meudelian inheritance might he explained. In the hybrid 

 the pair of fused chromosomes, representing the pres- 

 ence and absence of a character, is represented by the 

 black and white semicircles fused together. Should 

 their separation occur along the line of fusion (first line) 

 as demanded by the theory of pure gametes, there will 

 result after two divisions two chromosomes bearing 

 the positive character (or briefly the black chromo- 

 somes), and two without (or the white chromosomes). 

 These are represented for the egg in the upper line by 

 the four semi-circles ; and the similar cells for the male 

 by the four similar semi-circles in the line below. 

 Chance combinations will give three classes of individu- 

 als in the proportion of 1:2:1; or three with the domi- 

 nant to one with the recessive character. 8 



But should the pair of chromosomes fuse and not 

 separate at the line of fusion, the results are shown in 

 the second line, where the intersecting lines indicate 

 the plane of division. Again four classes of gametes 

 result, as shown in the upper line. If the same sort of 

 division occurs in the male, and fortuitous combinations 

 result, there will be the same three classes of individuals 

 as before, which gives the ratio of three dominant to one 

 recessive. 4 



The only division that will not give this result is that 



