CONJUGATION IN BLEPHARISMA UNDULANS 685 



that continued to live. Jennings, according to a recent paper 

 f'12), might argue that, since these 94 per cent of ex-conjugants 

 die, conjugation does not iniplj' rejuvenescence as Biitschh, 

 Maupas, and others have maintained. The continued hfe of 

 the 6 per cent, on the other hand, indicates that these varied 

 in some way from the others and represented a different mix- 

 ture of germ plasms. If we go back to the original records of 

 these 6 per cent we find that in no case, either exogamous or 

 endogamous, did both individuals of the syzygy continue to 

 hve, one lived, the other died after from one to thirteen divi- 

 sions. It is evident then, that even the admixture of the germ 

 plasms from the same cells is not equally potent. The result 

 may be interpreted either as a fortunate combination of pro- 

 nuclei, or as a particularly favorable cytoplasmic medium in 

 which the syncaryon acts, or both together. In any case it 

 may be granted that conjugation does involve the possibility 

 of increased variabihty, but this does not exclude the older view 

 of rejuvenescence or renewal of vitality tlirough conjugation. 

 We have repeatedly shown that a change in the chemical com- 

 position of the medium will counteract a period of depression 

 in organisms maintained on a constant diet, and renew the 

 vitahty, as indicated by the increased division rate. Engel- 

 mann ('76) early showed that conjugation results in the 'reor- 

 ganization' of the cell, and it is now a well-known fact that in 

 this process of reorganization the old macronucleus fragments 

 and ultimately disappears in the cytoplasm. This disappear- 

 ance must give rise to a great increase in the nucleo-protein 

 content of the cell, therefore to a new chemical composition 

 of the cell as a whole. We have recently shown that, under 

 certain conditions, nucleo-proteids (especially the purines), 

 have a markedl}'- stimulating effect on the rate of cell division 

 (Calkins, Bullock and Rothenburg '12). With this chemical 

 change in the cell there is a condition which, theoretically, 

 should work in the same general way as a chemical change in 

 the surrounding medium and give rise to a renewal of vitality. 

 The syncaryon in Paramecium caudatum, as we have seen, 

 divides three times wdthout cell division, and eight nuclei are 



