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 “reduplication.”” The term is applied 
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 two segregating divisions occur 
at first, producing the cells ABCc, AbCe, 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 lines 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 lines of cells reduplicate in a way just 
opposite to that in an individual which received Ab 
