236 BIOLOGY: GENERAL AND MEDICAL 



The theories most concordant with modern scientific 

 information are McClung's theory of the x-element and 

 the Mendelian theory. These are not discordant the- 

 ories, and both may contain the truth; the former is a 

 qualitative, the latter a quantitative demonstration of 

 what may take place. 



Man and Mam- 



REFERENCES. 



O. HERTWIG: "Text-book of the Embryology of 



mals." Translated by E. L. Mark, N. Y. 

 JOHN C. HEISLER: "A Text-book of Embryology," Phila. 

 L. P. McMuRRicn: "The Development of the Human Body," 



Philadelphia, 1904. 

 C. S. MINOT: "A Laboratory Text-book of Embryology," Phila., 



1903. 



A. M. MARSHALL: "The Frog, " etc., N. Y., 1906. 

 C. E. McCLUNG: The Biological Bulletin, 1902, iii, 43. 

 E. B. WILSON: "Recent Researches on the Determination and 



Heredity of Sex," 1909. 

 The Encyclopedia Britannica: Article on Sex. 

 T. H. MORGAN: "Experimental Zoology." The Biological Bulletin, 



1902, iii, 56. 

 L. DONCASTER: "Determination of Sex," Cambridge University 



Press, 1914. 



