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, i.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 



