686 GARY N. CALKINS 



formed. Four of these nuclei become macronuclei, four micro- 

 nuclei. These are formed during the process of disintegration 

 and absorption of the old macronucleus. Then follows two 

 divisions of the cell, resulting in four individuals, each with 

 the normal nuclear relations. Each cell is now a new individual 

 with renewed chemical basis and newly combined nuclei. The 

 power to vary follows from the increased powers of metabolism, 

 and it seems to us that the phenomena of conjugation are more 

 reasonably interpreted as processes which have developed for 

 rejuvenating effects whereby powers of metabolism, irritability, 

 reproduction, and variation are reinvigorated, rather than as 

 processes for engendering variations. If it is argued that 100 

 per cent of Blepharisma die after conjugation and, therefore, 

 that rejuvenescence is not an effect of conjugation, the same 

 argument may be returned and the question asked: Where does 

 variation come in when 100 per cent die? We believe that 

 unknown, probably cultural, conditions enter into the problem 

 and make conjugation even more difficult to interpret under 

 either hypothesis. 



June, 1912. 



LITERATURE CITED 



Anigstein, p. 1912 Beobachtungen . iiber zwei neuen Ciliatenarten. Arch, 

 f. Prot. 



Baitsell, G. a. 1911 Conjugation of closely-related individuals of Stylon- 

 ychia. Proc. Soc. Exp. Biol. Med., vol. 8, p. 74. 



Balbiani, E. G. 1860 Recherches sur les phenomenes sexuelles des Infusories. 

 Jour, de la Physiologic, torn. 4. 



BtJTSCHLi, O. 1876 Studien iiber d. erst. Entwickelungsvorgan. d. Eizelle. 

 d. Zelltheilung u. die Conjugation der Infusorien. Abh. d. Sencken- 

 berg. naturforsch. Gesell. Frankfurt a/M., Bd. 10. 



Calkins, G. N. 1903 Studies on the life history of Protozoa, I. Arch. f. Ent- 

 wicklungsmechan., Bd. 15, p. 139. 



Calkins, G. N., Bullock, F. D. and Rothenberg, G. L. 1912 The effects of 

 chemicals on the division rate of cells. Jour. Infect. Diseases, May. 



Cull, Sara W. 1907 Rejuvenescence as a result of conjugation. Jour. Exp. 

 Zool., vol. 4. 



