FERTILITY IN ANIMALS 561 
(a) The Sex Factors.—In the fowl the type of sex-inheritance is that 
designated WZ in Morgan’s terminology. Females are heterozygous 
for the sex-factor; 7.e., they are WZ in constitution, whereas males are 
homozygous, ZZ. W like Y in the XY type is neutral and carries no 
demonstrable factors. 
(b) A fecundity factor, L, which determines a winter egg production of 
something less than thirty eggs. It is dominant over the allelomorph 
l, which is present in fowls 
which produce no eggs 
during the winter season, 
but the homozygous con- 
Taste LXXIV.—Generic ConstItUrions OF 
BarreD PtymourH Rock Mags FOR 
Frecunpity Factors 
dition LZ does not con- ie: Genetic Aer are 
dition a higher winter egg ; ponsttwtione 20) Senta Gece es 
production than does the 1 | (ZM)(ZM)LL |(ZM)L 
heterozygous condition Ll. 2 | (ZM)(Zm)LL |(ZM)L, (Zm)L 
(c) A Sex-linked Fe- 3 | (ZM)(ZM)LI |\(ZM)L, (ZM)I1 
cundity Factor, M.—Like 4 ees ae (4M)1, (Zm)L, (Zm)l 
: : 5 | MY) M) 
iy He oalseagumertes Newey Faieen Cae (Zm)l 
winter egg production of Ha CAC NaEN ICE 
something less than thirty —8_ | (Zm)(Zm)LI_|(Zm)L, (Zm)l 
eggs. With L, however, 9 | (Zm)(Zm)lul (Amy 
it gives a winter egg pro- 
duction of over thirty. 
Pearl was able to classify the individuals which he used in his ex- 
periments into classes according to their zygotic constitutions. For the 
sake of clearness these classes are given in Tables LXXIV, LXXV, 
Taste LX XV —Genetic ConsriTuTION or BAarreD Piymoutu Rock FEMALES FOR 
Frcunpity Factors 
Class Genetic constitutions Z gametes | W gametes Winter egg production 
1 (ZM)WLl | (ZM)L, (ZM)I WL, WI Over 30 eggs 
2 (ZM)WLL | (ZM)L WL Over 30 eggs 
3 (Zm) WLI (Zm)L, (Zm)l WL, WI Under 30 eggs 
4 (Zm) WLL (Zm)L WL Under 30 eggs 
5 (Zm) Wil (Zm)l Wil No eggs 
6 (Z2M)Wi: (Zm)l Wi Under 30 eggs 
LXXVI,andLXXVII. These tables represent genetic constitutions which 
were realized and recognized during the course of the experiments. It 
will be observed that among the Barred Plymouth Rocks every possible 
genetic constitution was represented, but among the Cornish Indian 
Games the factor MM was not contained in any individual. 
36 
Digitized by Microsoft® 
