706 SEXUALITY 



requires identification of all sex differences with male and female. There 

 may be two kinds of copulation-conditioning factors: one functioning in 

 bringing together the cells, the other in bringing together their nuclei. 

 In Chlanjydonionas and the Vorticellidae, the two kinds of nuclear fac- 

 tors operate in different kinds of cells; in Parana eciuin and most other 

 ciliates, both kinds of nuclear factors operate in each of the kinds of 

 cells. Thus by abandoning the pure assumption that sex differences, 

 wherever found, must always be fundamentally the same (male and 

 female), the conflict between sex differences in nuclei and sex differences 

 in cells disappears. 



Literature Cited 



Calkins, G. N. 1920. Uroleptns mobilis Engelm. III. A study in vitality. 

 J. exp. Zool, 34: 449-70. 



1926. The Biology of the Protozoa. Philadelphia and New York. 



Calkins, G. N., and S. W. Cull. 1907. The conjugation of Paramecium 



auvelia {caudatum) . Arch. Protistenk., 10: 375-415. 

 De Garis, C. F. 1935. Heritable effects of conjugation between free individuals 



and double monsters in diverse races of Parawedum caudatum. J. exp. 



Zool., 71: 209-56. 

 Diller, W. F. 1936. Nuclear reorganization processes in Paramecium aurelia, 



with descriptions of autogamy and "hemixis." J. Morph., 59: 11-68. 

 Doflein, F. 1907. Beobachtungen und Ideen iiber die Konjugation der In- 



fusorien. S. B. Ges. Morph. Munchen, 23: 107-14. 

 Dogiel, V. 1925. Die Geschlechtsprozesse bei Infusorien (speziell bei den 



Ophryoscoleciden), neue Tatsachen und theoretischc Erwagungen. Arch. 



Protistenk., 50: 283-442. 

 Enriques, P. 1908. Die Conjugation und sexuelle Differenzierung der In- 

 fusorien. Zweite Abhandlung. Wiederconjugante und Hemisexe bei 



Chilodoii. Arch. Protistenk., 12: 213-76. 

 Finley, H. E. 1939. Sexual differentiation in VorticeUa m'lcrostoma. J. exp. 



Zool., 81: 209-29. 



1939b. Further observations upon sexual differentiation in VorticeUa 



microstoma. Anat. Rec, 75, (suppl.), p. 85. 



Geitler, L. 1932. Der Formwechsel der pennaten Diatomeen (Kieselalgen). 



Arch. Protistenk., 78: 1-226. 

 Giese, A. C. 1938. Race and conjugation of Paramecium. Physiol. Zool., 11: 



326-32. 



1939. Studies on conjugation in Paramecium multimicronucleatum. 



Amer. Nat., 73: 432-44. 



Giese, A. C, and M. A. Arkoosh. 1939. Tests for sexual differentiation in 



