ii8 Outline of Genetics 



seeds of Oe. Lamarckiana are empty. De Vries explains this 

 by saying that Lamarckiana produces two kinds of gametes, the 

 typical or laeta and the veliUlna. Each gamete has a lethal factor 

 closely linked with the character factor. Heterozygous combina- 

 tions give good seeds, homozygous give sterile. If one of the two 

 lethal factors becomes "vital," the Oe. laeta or Oe. velutina muta- 

 tion appears. 



LITERATURE CITED 



1. Baur, Erwin, Mutationen von Antirrhinum majus. Zeit. 

 Induct. Abstamm. Vererb. 19:177-193.^^^. 10. 1918. 



2. Blakeslee, a. F., Belling, John, and Farnham, M. E., 

 Chromosomal duplication and Mendelian phenomena in 

 Datura mMidMis. Science 52:388-390. 1920. 



3. Bridges, Calvin B., \'ermilion-deficiency. Jour. Gen. 

 Physiol. 1:645-656. 1919. 



4. , The developmental stages at which mutations occur 



in the germ tract. Proc. Soc. Exp. Biol, and Med. 17:1-2. 

 1919. 



5. De Vries, Hugo, Phylogenetische und gruppenweise Artbil- 

 dung. Flora 11-12:208-226. 1918. 



6. Morgan, T. H., Evolution by mutation. Sci. Monthly 5: 

 46-53. 1918. 



7. MuLLER, H. J., Genetic variability, twin hybrids, and con- 

 stant hybrids, in a case of balanced lethal factors. Genetics 

 3: 42 2-4gg. fig. I. 1918. 



8. , Further changes in the white-eyed series of Drosophila 



and their bearing on the manner of occurrence of mutation. 

 Jour. Exp. Zool. 31:443-473.^^. 3. 1920. 



9. — -, Variations due to change in the individual gene. 



Amer. Nat. 56:32-50. 1922. 



10. — , and Altenburg, E., A study of the character and 



mode of origin of eighteen mutations in the X chromosome of 

 Drosophila. Anat. Rec. 20:213. 1921. 



11. Nilsson-Ehle, H., Multiple allelomorphe und Komplexmu- 

 tationen beim Weizen. Hereditas 1:227-311. 1920. 



12. Zeleny, Charles, The direction and frequency of mutation 



in a series of multiple allelomorphs. Anat. Rec. 20:210-211. 

 1921. 



