74 GEOEGE ALFRED BAITSELL 



and that it bears no relation, in this form at least, to a particular 

 period of a 'life-cycle.' 



11. It is suggested that the infertility of the syzygies in these 

 cultures is the result of the fact that the gametes had an identical 

 environmental history. 



LITERATURE CITED 



Baitsell, G. a. 1911 Conjugation of closely related individuals of Stylonychia. 

 Proc. of the Society for Exper. Biology and Med., vol 8, no. 5. 



BtJTSCHLi, O. 1876 Studien iiber die ersten Entwickelungsvorgange der Eizelle, 

 der Zelltheilung and der Konjugation der Infusorien. Abh. d. Senckenb. 

 nat. Gesellsch. Frankfurt a. M., Bd. 10. 



Calkins, G. N. 1902 a. Studies on the life history of Protozoa. I. The life-cycle 

 of Paramaecium caudatum. Archiv. f. Entw. der Org. , vol. 15, no. 1. 



1902 b. Studies on the life-history of Protozoa. III. The six hundred 

 and twentieth generation of Paramaecium caudatum. Biol. Bull., vol. 3, 

 no. 5. 



1904 Studies on the life history of Protozoa. IV. Death of the A-ser- 

 ies of Paramaecium caudatum. Conclusions. Jour. Exp. Zool., vol. 1, 

 no. 3. 



1912 Paedogamous conjugation of Blepharisma. Science, vol. 35, 

 no. 899, March 22. 



Calkins, G. N., AND Cull, S.W. 1907 Conjugation of Paramaecium caudatum. 

 Archiv. f. Protistenk., Bd. 10. 



Cull, S. W. 1900 Rejuvenescence as^ result of conjugation. Jour. Exp. Zool., 

 vol. 4, no. 1. 



Enriques, p. 1905 Ancora della degenerazione senile negli Infusori. Rendic 

 Accad. Lincei (5) vol 14. 



Gregory, L. H. 1909 Observations on the life history of Tillina magna. Jour. 

 Exp. Zool., vol. 6, no. 3. 



Jennings, H. S. 1910 What conditions induce conjugation in Paramaecium? 

 Jour. Exp. Zool., vol 9, no. 2. 



1911 Assortive mating, variability and inheritance of size, in the con- 

 jugation of Paramaecium. Jour. Exp. Zool., vol. 11, no. 1. 



1912 Age, death and conjugation in the light of work on the lower 

 organisms. Pop. Sci. Monthly, vol. 80, no. 6. 



JouKowsKY, D. 1898 Beitrage zur Frage nach den Bedingungen der Vermeh- 

 rung und des Eintrittes der Konjugation bei den Ciliaten. Verh. Nat. 

 Med. Ver. Heidelberg, Bd. 26. 



