1. Cutler, D. W. andDoncaster, L. “On the Sterility of the Tortoise-shell Tom Cat.”Journ. of Genetics, Vol. v. 1915.
2. Federley, H. “Das Verhalten der Chromosomen bei der Spermatogenese von Pygaera.”Zeitschr. f. indukt. Abstamm., Vol. ix. 1913.
3. Guyer, M. F. “Spermatogenesis of Normal and Hybrid Pigeons.”Thesis, University of Chicago, 1900.
4. - “Sex of Hybrid Birds.”Biol. Bull., Vol. xvi. 1909.
5. - “Studies on the Chromosomes of the Common Fowl as seen in Testes and in Embryos.”Biol. Bull., Vol. xxxi. 1916.