RELATION OF RHYTHMS AND ENDOMIXIS. 47 



teen) was due to chance, and not to any inherent constancy in the 

 periodicity itself. 



Undoubtedly there is more or less regularity in endomixis, 

 just as in any other physiological process (cell division, repro- 

 duction, respiration, excretion, etc.) ; but to prove that this has a 

 fixed time periodicity, which, unlike that of other physiological 

 processes, cannot be modified by environment, will require much 

 stronger evidence than Woodruff has as yet presented. His own 

 data are contradictory and my results point very strongly to an 

 opposite conclusion. 



LITERATURE CITED. 

 Hertwig, R. 



'88-'8g Uber die Conjugation der Infusorien. Abhdl. Math. Phys. Cl. Kgl. 



Bayr. Akad. Wiss., Bd. 17, pp. 151-234. 

 Kasanzeff, W. 1 



'01 Experimentelle Untersuchungen liber Paramecium caudatum. Inaug. Diss., 



Zurich. 

 Popoff, M. 



'09 Experimentelle Zellstudien, III. Uber einige Ursachen der physiologischen 



Depression der Zelle. Archiv fur Zellforschung, Bd. 4, pp. 1-43- 

 Sun, A. 



'12 Experimentelle Studien iiber Infusorien. Archiv fiir Protistenk., Bd. 27, 



pp. 207-18. 

 Woodruff, L. L. 



'05 An experimental study on the life history of hypotrichous Infusoria. Jour. 



Exp. Zool., vol. 2, pp. 585-632. 

 'i7a Rhythms and endomixis in various races of Paramecium aurelia. BIOL. 



BULL., Vol. XXXIII., pp. 51-56. 

 'i7b The influence of general environmental conditions on the periodicity of 



endomixis in Paramecium aurelia. Ibid., pp. 437-62. 

 Woodruff, L. L., and Erdmann, R. 



'14 A normal periodic reorganization process without cell fusion in Paramecium. 



Jour. Exp. Zool., vol. 17, pp. 425-520. 

 '16 The periodic reorganization process in Paramecium caudatum. Ibid^ 



vol. 20, pp. 59-98. 

 Young, R. T. 



'17 Experimental induction of endomixis in Paramecium aurelia. Jour. Exp. 

 Zool., vol. 24, pp. 35-53- 



1 Not seen by me. 



