The Life History of Tillina Magna 429 



13 Each protozoan individual has its own characteristic degree 

 of sensitiveness that differs from all others of the same family, as 

 well as from all others of different species. 



14 Actual measurements of nuclear and protoplasmic size, 

 at different stages in the life history, show that there is no relation 

 between an excess of nuclear material and a period of low vital- 

 ity. Such periods of weakness may or may not be accompanied 

 by changes in the size relations of the nuclear and cytoplasmic 

 material, in no way are they caused by such variations. The 

 true cause must be sought in the physiological not morphological 

 changes taking place within the cell. 



Zoological Laboratory. 



Columbia University, 



January, 1909. 



LITERATURE 



Bessenberger, E. '03 — Ueber Infusorien aus asiatischen Anuren. Arch. f. Pro- 



tistenk. 

 BovERi, Th. '05 — Zellenstudien, v. 



BiJTSCHLi, O. '76 — Studien iiber die ersten Entwickelungsvorgange der Eizelle 

 der Zelltheilung, und der Conjugation der Infusorien. Abh. d. 

 Senckenb. nat. Gesellsch. Frankfurt a.M., x. 

 '83 — Protozoa. Bronn's Klassen und Ordunngen des Thierreichs. 

 '94 — Protoplasm and Microscopic Foams. 

 Calkins, G. N., 'oi — The Protozoa. Columbia University Press. 



'02 — Studies on the Life History of Protozoa. I. The Life Cycle of 

 Paramoecium caudatum. Arch. f. Entwickelungsmech., xv. 

 Calkins and Lieb '02 — Studies on the Life History of Protozoa. H. The Effect 

 of Stimuli on the Life Cycle of Paramcecium caudatum. Arch, 

 f. Protistenk, i. 

 Calkins, G. N. '02— Studies on the Life History of Protozoa. HL The Six- 

 hundred and Twentieth Generation of Paramoecium caudatum. 

 Biol. Bull., iii. 

 '04 — Studies on the Life History of Protozoa. IV. The Death of the 

 "A" Series of Paramoecium caudatum. Conclusions. Journ. of 

 Exp. Zool., i. 

 '06 — The Protozoan Life Cycle. Biol. Bull., ii. 



