Neo-Mendelism 



87 



grain and red cob of the first mentioned experiment 

 were not produced by a single determiner, but by 

 two determiners coupled together in inheritance. It is 

 as if the two chromosomes concerned had a bond between 

 them which kept them together during the reduction 

 division, and made them pass side by side into the 

 same gamete. A diagram will illustrate this situation 

 (fig. 20). The only unusual thing in this diagram is 

 the bond which holds together the chromosome carrying 



Dominant Parent 



with Red Seeds 



and Cobs 



Recessive Parent 



with White Seeds 



and Cobs 



F, (Red Seeds and Cohs) 



Fig. 20. — Diagram representing, in a somewhat obvious way, how 

 the behavior of "coupled characters" might be visualized. 



the determiner for red seeds and the chromosome 

 carrying the determiner for red cob. A peculiar function 

 of the bond, however, appears in the reduction division 

 in coimection with gamete formation by the Fj genera- 

 tion. 



In the case of a dihybrid in which two characters 

 are involved the situation developed by the reduction 

 division will be recalled (fig. 21). It will be noted 

 that there are four chances of pairing off by the four 

 scattered chromosomes. The chances of getting a 

 gamete with the two determiners is no greater than 



