304 HEREDITY IN THE PROTOZOA 
their later rates of division. He compared their 
rates with the rates of sister individuals that were 
allowed to complete conjugation and then separate. 
He found that the split-pairs divide more rapidly 
than the ex-conjugants, and also that they show 
greater variation between the members of the pair 
than do the ex-conjugants. He interprets the 
result to mean that the ex-conjugants should be 
expected to be more alike in so far as they have 
each received a part of the other. This would only 
be expected, however, on the supposition that re- 
duction did not take place at the last micronuclear 
division, 7.e., just previous to conjugation; for, if 
reduction had occurred then, the migrating nucleus 
of individual A, received by the mate B, would not, 
on the average, tend to be any more like the station- 
ary nucleus of A than it is like either of the nuclei 
of B, and so the ex-conjugants would be no more 
alike than members of split-pairs. It may seem 
that a test as to whether any of the micronuclear 
divisions preceding conjugation are reductional might 
be made if the rate of division of the split-pairs 
were compared with that of the original strain from 
which they were derived. Jennings has made such 
a comparison and finds no difference between the 
rate of fission of the split-pairs and the rate of 
division of other individuals of the same culture 
that had not conjugated. This evidence appears 
to mean that no change in the hereditary complex 
takes place during the three micronuclear divisions 
preceding interchange; but this conclusion may 
