.HOUWINK’S EXPER. CONC. THE ORIGIN OF SOME DOMESTIC ANIMALS 273 
Now a silver hen e. g., in this case a silver partridge or silver duck- 
wing, crossed with a gold cock must produce gold hens and silver cocks, 
so that the cock can not have been gold, as both silver and gold cocks 
were produced. Nor can the cock have been silver, because in that case 
the whole progeny should have been silver. Neither can we get the 
result obtained if the cock were heterozygous silver-gold, as in that case 
we should have obtained silver and gold hens, but cocks which were all 
silver. It is therefore probable that the gold cocks, said to have been 
obtained from this experiment, came from some other experiment and 
were mixed up with the progeny of this series, after stuffing, e. g. were 
wrongly numbered. If this is the real explanation, the result: gold pul- 
lets and silver cockerels, is what we would expect from the cross of a 
silver hen and a gold cock, so that it would follow that the Gallus 
aeneus used, did not contain a silver-factor. 
There is however another peculiarity to be considered. We have seen 
that our Gallus aeneus was cross-barred. The barring factor is a sex- 
limited factor also. If the G. aeneus used had been homozygous for the 
barring factor the whole of the progeny should have been barred, this 
has not been the case, but among the silver cockerels obtained (we ex- 
clude the gold ones for the reason mentioned above) two are barred e. g. 
194.4 and 194.6. They have a general pattern close to that of a duck- 
wing, but with a decided varius-influence in the hackles on which, as 
well as on the tailcoverts, the barring is very distinct. The other silver 
cockerel 194.20 is silver also, but with more brown than the two just 
mentioned; it might be characterised as a duckwing with a considera- 
ble amount of brown; its hackles are very much like those of a bankiva 
in shape and the animal is not barred. 
The Gallus aeneus used, consequently was heterozygous for the 
barring factor and should have given both barred and unbarred Fro- 
geny of both sexes; that no barred pullets were born was probably due 
to the small number raised. 
Our Gallus aeneus therefore must have been, either a cross between a 
barred strain of domestic poultry and Gallus varius, or it may have 
derived its barring factor from the female of Gallus varius. 
However this may be, the results obtained prove, that hybrids be- 
tween domestic poultry and Gallus varius segregate. 
Genetica VI 18 
