H. E. Jordan 81 



pedigrees of human twiimiiig that the exjjlaiiation of ordinary and 

 duplicate twins is probably not as simple a matter as has been supposed. 

 It would appear that the sperm is as potent as the egg, in determining 

 twins, either ordinary or identical. 



LITERATURE CITED. 



AssHETON, Richard. " Fission of Embryonal Area in JIammals ; Summary." 



Journ. Roy. Micr. Soc. Oct. 1913. 

 Davenport, C. B. Heredity in Relation to Eugenics. H. Holt and Co., N.Y., 1911. 

 Elderton, Ethel M. On the Marriage of First Cousins. Eugenics Laboratory 



Lecture, Series V, Dulau and Co., London, 1911. 

 Hurst, C. C. " Mendelian Heredity in Man." Eugenics Reoiew, April, 1012. 

 Jordan, H. E. "The Liheritance of Lefthaudedness." American Breeders Maga- 

 zine, Vol. n. Nos. 1 and 2, 1911. 

 . "Studies in Human Heredity." Bulletin of the Philosophiad Society, 



Univ. of Virginia, Scientific Series, Vol. i. No. 12, July, 1912. 

 Oliver, Jame.s. "The Hereditary Tendency to Twinning." Eugenics Revieu', April 



and July, 1912. 

 Patterson, J. T. "A Preliminary Report on the Demonstration of Polyembryonic 



Development in the Armadillo." Anat. Anz. Bd. xli. No. 13, 1912. (Full 



report, Journ. Morph. Vol. xxiv. No. 4, 1913.) 

 Stier, Ewald. Untersuchungcn iiber Linkshdndigkeit. Gustav Fischer, Juna, 1911. 



Journ. of Gen. iv 



