LINKAGE 75 



tions AB, Ab, aB, and ab, respectively. These cells 

 then proceed to divide, the number of divisions not 

 being the same for each, which results in the produc- 

 tion of more of some kinds of cells than of others. 

 But this multiplication must be assumed to be a 

 symmetrical process, since the observed number of 

 AB gametes equals the number of ab, and similarly 

 Ab equals aB. The whole process just described 

 is known as ^^reduphcation." The term is apphed 

 to the same cases as those included under the name 

 of linkage. 



When three pairs of factors are involved in the same 

 ^'reduplication series" Bateson supposed at one time 

 that they are segregated at three successive cell 

 divisions, after which the eight resulting cells divide 

 at unequal rates. Later Trow suggested for such a 

 case that perhaps only tw^o segregating divisions occur 

 at first, producing the cells ABCc, AbCc, aBCc, and 

 abCc, which may then multiply so as to give the 

 proper proportions for the A and B combinations. 

 After this there occurs in every cell a division which 

 segregates C and c. The resulting cells then divide 

 again so as to produce the observed relations be- 

 tween the C pair and the other factors. 



The nature of the factors themselves in the differ- 

 ent fines of cells resulting from segregation can not 

 be supposed to determine the difference in the number 

 of times that these lines divide, because if an indi- 

 vidual has received AB from one parent and ab from 

 the other, the fines of cells redupficate in a way just 

 opposite to that in an individual which received Ab 



