276 Preponderance of Males and Females in Fish 



a large preponderance of males, often larger than the previous pre- 

 ponderance of females. No non-viable zygotes are produced. 



Sex-ratio of first Swung-back sex-ratio Sex-ratio of SwuDg-back Final sex-ratio 



abnormal after first third abnormal sex-ratio after (all ZZ in 



generation generation generation third generation constitution) 



? 



I 1 



\ 1 



i 1 



A 1 



<? $:c? ?:<? ?:c? ?:(?' 



005 1:2-8 1 : 0-09 1 : 8-94 1 : 0-11 



014 1:2-5 1 : 0-24 1 : 643 1 : 0-33 



0-33 1:20 1 : 0-55 1 : 3-50 1 : 100 



0-60 . 1:1-5 1 : 0-91 1 : 181 1 : 3-00 



0-82 1:1-2 1 : 098 1 : 124 1 : 900 



Thus, while the initial sex-ratio of course shows a preponderance of 

 females, the final sex-ratio shows a preponderance of males when p<\. 



(II) If the disturbing factor is such as to convert zygotes of female 

 constitution into somatic males (as in Hertwig's frogs), the above 

 calculations must be reversed, those for XX, XY organisms now 

 applying to those of formula ZW, ZZ, and vice versa. The limiting ratio 

 will in this case occur in organisms of the ZZ, ZW type, whereas in 

 those oi XX, XY type, the process will continue until only individuals 

 of XX constitution are found. 



LITERATURE. 



BouLENQER, E. G. ('12.) Proc. Zool. Soc. 1912 (2), p. 906. 



DoNCASTER, L. ('12.) Science (N.S.), Vol. xxxvi. 1912, p. 282. 



Qerschler, M. W. ('14.) Zeitschr.f. hxdiikt. Abst. u. Vererhungslehre, Bd. xii. 1914. 



GoLDSCHMiDT, R. ('16.) Amer. Nat. Vol. l. 1916. 



('19.) Biol. Zentralhl. Bd. xxxix. 1919, p. 498. 



Harper, E. H. ('04.) Amer. Journ. Anat. Vol. in. 1904. 



Harrison. ('19.) Journ. Genetics, Vol. ix. 1919. 



Hertwig, R. ('07.) Verh. d. Deutsch. Zool. Oes. Bd. xvii. 1907. 



Keilin, D. and Nuttall, G. H. F. ('19.) Parasitology, Vol. xi. 1919. 



King, H. D. ('12.) Anat. Record, Vol. vi. 1912. 



KuscHAKEWiTSCH, S. ('10.) Festschrift fur R. Eertwig, 1910, Bd. ll. 



LiLLiE, F. R. ('17.) Journ. Exp. Zool. Vol. xxiil. 1917. 



Morgan, T. H. ('19.) The Physical Basis of Heredity, Lippincott, 1919. 



Pearl, R. and Parshley, H. M. ('13.) Biol. Bull. Vol. xxiv. 1913. 



Riddle, 0. ('16). Amer. Nat. Vol. l. 1916. 



Shull, G. H. ('14.) Zeitschr.f. Indukt. Abst. u. Vererbungslehre, Bd. xil. 1914. 



Smith, G. W. ('06.) Rhizocephala, Berlin, 1906. (Fauna u. Flora des Golfes v. Neapel, 



XXIX.) 



Steinach, E. ('12.) Pfluger's Archiv f. d. Oes. Physiol. Bd. cxLiv. 1912. 



('13.) Zentralblatt f. Physiol. Bd. xxvii. 1913, p. 717. 



Strasburger, E. ('00.) Biol. Centralbl. Bd. xx. 1900. 



('10.) Jahrb.f Wiss. Bot. Bd. xlviii. 1910. 



Strong, R. M. ('12.) Biol. Bull. Vol. xxin. 1912. 



