Sex Dclermi)hitiou 203 



certain chromosome sets. This. I)y inlro<iucing a relatively 

 greater number of genes which have a positive inlluence (or 

 negative, as the case may be), may modify the degree of expression 

 of the character in question so that it shows a grade not previously 



seen. 



LITERATURE Clli:i) 



1. Allen, Charles E., A chromosome ditTercncc correlated with 

 sex differences. Science 46:466-467. 1917. 



2. Blakeslee, A. E., Sexual reproduction in the Mucorincae. 

 Proc. Amer. Acad. 40:205-319. 1914. 



3. , DifTerentiation of sex in thallus gametophytc and 



sporophytc. Bot. Gaz. 42: 161-178. 1906. 



4. , Sex in Mucors. Ann. Rcpt. (\arnegie Inst. 1920: 



128-130. 



5. Bridges, C. B., Non-disjunction as proof of the chromosome 

 theory of heredity. Genetics i : 1-52. 1916. 



6. , Triploid intersexes in Drosopliila nielanogaster. 



Science 54:252-254. 1921. 



7. , The origin of variations in sexual and sex-limited 



characters. Amer. Nat. 56:51-63. y/g^. 7. 192:. 



8. BuRGEFF, H., tJber Sexuahtat, \'ariabilitat. und N'crerbung 

 bei Phycomyces nitens. Ber. Deutsch. Bot. (iesell. 30:679- 

 685. 1912. 



9. , Sexuahtat und Parasitismus bei ^lucorincen. Ber. 



Deutsch. Bot. Gesell. 38:318-328. 192 1. 



10. Castle, W. E., The I'-chromosome type of sex-linked inherit- 

 ance in man. Science 55:703-704. 1922. 



11. CoRRENS, C, Die Konkurrenz der mannlichen und dcr 

 weiblichcn KeimzcUen und das Zahlenverhiiltnis iler beiden 

 Geschlechter. Naturwissenschaf ten 6:277-280. 1918. 



12. , and GoLDSCHMiDT, R., Die Nererbung u. Hestimmung 



des Geschlechts. Berlin. 1913- 



13. GoLDSCHMiDT, R.. Untcrsuchungcu iiber Interse.xualital. 

 Zeit. Indukt. Abstamm. \'ererb. 23:1-199. ph. ::. figs. S4. 

 1920. 



14. Hertweg, R., \'erhandl. Deutsch. Ztx)l. (iesell. 1906; see 

 also Biol. Centralbl. 32: 1. 191 2. 



