336 HELEN DEAN KING 
strongly suggest that in Bufo sex does not depend exclusively on 
the spermatozoan, but that it is determined by the egg alone, 
or by both egg and sperm. It would appear, also that sex can be 
influenced by decreasing the water content of the egg at or before 
the time of fertilization. 
Hertwig’s (’06) theory that sex is determined by the mass rela- 
tion between the chromatin and the cytoplasm seems to offer a 
tentative explanation of these results, if it is applied to the con- 
ditions existing in the zygote and not to those in the ripe, unfer- 
tilized egg. Until these experiments have been repeated and 
extended, however, it will be useless to attempt the formulation of 
a theory of sex-determination that will explain these results and 
bring them in harmony with those that have been obtained by 
other investigators in this field. 
LITERATURE CITED 
BautzEr, F. 1909 Die Chromosomen von Strongylocentrotus lividus und Hchi- 
nus microtuberculatus. Arch. Zellforsch., Bd. 2. 
Brauaszewicz, K. 1908 Beitrige zur Kenntniss der Wachstumvorgiinge bei 
Amphibienembryonen. Bull. Inter. de l’Akad. Sci. de Cracovie. 
Math.-Natur. Classe. 
Davenport, C. B. 1897 Experimental morphology. The Macmillan Company. 
vVoN GriesHEIM, A. 1881 Ueber die Zahlenverhiltnisse der Geschlechter bei 
Rana fusca. Arch. gesammte Physiol., Bd. 26. 
Hertwia, R. 1906 Weitere Untersuchungen ueber das Sexualitaitsproblem. 
Verhandl. deutsch. zo6l. Gesellsch. 
Kine, H. D. 1901 The maturation and fertilization of the eggs of Bufo lentigi- 
nosus. Jour. Morph., vol. 17. 
1907 a The spermatogenesis of Bufo lentiginosus. Amer. Jour. Anat., 
vol. 7. © 
1907 Food as a factor in the determination of sex in amphibians. 
Biol. Bull., vol. 18. 
1909 Studies on sex-determination in amphibians. II. Ibid., vol. 16. 
1910 Temperature as a factor in the determination of sexin amphibians. 
Ibid., vol. 18. 
1911 Studies on sex-determination in amphibians. IV. The effects 
of external factors, acting before or during the time of fertilization, on 
the sex ratio of Bufo lentiginosus. Ibid., vol. 20. 
Logs, J. 1906 The dynamics of living matter. The Macmillan Company. 
Pritcer, E. 1882 Ueber die das Geschlecht bestimmenden Ursachen und die 
Geschlechtsverhiltnisse der Frosche. Arch. gesammte Physiol., Bd. 29. 
Witson, E. B. 1910 Selective fertilization and the relation of the chromosomes 
to sex-determination. Science, vol. 32. 
