UEOLEPTUS MOBILIS ENGELM. 455 



The other companion experimental series, the PX7 series, was 

 obtained from a pair of conjugating individuals in which the 

 nuclei were in the stage of the third maturation division. The 

 individual in culture regenerated in six hours and reorganized in 

 seven days (fig. 4). The shorter time required for reorganiza- 

 tion is worthy of note, as it was possibly due to the late stage of 

 conjugation at the time of cutting. Its average division rate 

 for the first sixty days of life was 16.7 times -in ten days, while 

 that of the parent P series was 14.2 and that of the control 

 PV series was 15.5 times. Its division rate per ten days until 

 the death of the parent P series was 12.6 times as against 8.5 

 divisions for the parent series. The PX7 series, therefore, 

 showed increased vitality over the parent protoplasm not only 

 during the first sixty days of its life, but also throughout the 

 remaining life of the parent. It did not live as long as the com- 

 panion experimental series, however, dying out after 219 days 

 and 264 generations and outliving the parent by only sixty days, 

 hence its relative vitality, 64.5 per cent, was less than that of the 

 PXl and the PX7 series and much less than that of the parent 

 and that of the normal ex-conjugant control. 



The progeny obtained from these individuals which were cut 

 while conjugating were normal in every respect. Conjugation 

 tests made from time to time gave epidemics of conjugations 

 exactly as in cases of normal ex-conjugant series. Such con- 

 jugations were normal, and ex-conjugants obtained from them 

 gave rise to series which lived through normal life-cycles, although 

 the relative vitalitj^ was low in every case. 



Two such normal series were taken from the PX7 series in its 

 183rd generation on September 13, 1919, and in its 203rd genera- 

 tion on October 8th. These were the AX7 and the X7A series, 

 respectively. They lived for 165 and 125 division days, re- 

 spectively, and divided 191 and 163 times. The average division 

 rates per ten days for the first sixty days of life were 14 and 15.2, 

 respectively, as against 9.4 divisions and 5.4 divisions per ten 

 days for the parent PX7 series during the same periods. The 

 relative vitalities were low, amounting only to 52.7 per cent and 

 42.7 per cent. 



