HOUWINK’S EXPER. CONC. THE ORIGIN OF SOME DOMESTIC ANIMALS. 151 
Silky-mother. 
Cocks. Hens. 
413.4 413.8 
413.5 413.9 
413.6 413.10 
413.7 413.15 
413.11 413.16 
413.12 413.4 
413.13 624.5 
413.14 Oty NDE 
624.1 
624.2 
624.3 
11 
Or 11 cocks and 7 hens all with rose comb. 
First of all it is necessary now, to lay stress on the fact that 
our Silkies bred true in comb form. They always had the typical 
trifid rose comb and the jungle fowls never shew any deviation 
from their typical single comb. 
Yet there is no doubt that the Silky cocks we used, were 
heterozygous as far as the comb factors are concerned. They 
possessed a factor for single comb. 
The Silky hens we used, must have been homozygous for the 
rose comb (Silky-comb). Now, two things are possible. 
1°. The heterozygous state of our silky cocks was only an 
accident and the homozygous state of the hens also. But then 
sometimes Silkies with single comb from a mating of two hetero- 
zygous parents should have been born. This did not happen at 
all in our breeds. | 
2°. The heterozygous nature of the comb factors in Silky-cocks 
is the regular state. : 
In the pure breed, if the hens are homozygous, as ours proved 
to be, even if all the cocks are heterozygous with a factor for 
single comb, never a pullet with single comb will be born. 
The second supposition agrees with the results of our breeding 
experiments, the first doesn’t. Therefore we incline to suggest that 
Silky-cocks form two sorts of gametes and Silky hens only one. 
r 
