HOUWINK’S EXPER. CONC. THE ORIGIN OF SOME DOMESTIC ANIMALS 159 
on this point from our material but probably this character is ruled 
by more than one factor. 
Double-hallux. 
Our experiments gave only a confirmation of the results of 
other naturalists. The double-hallux is ‘dominant to normal toes. 
In our first cross Bankiva © X Silky ¢ (exp. 414) we used a 
Silky cock with 4 toes on both feet. The whole offspring without 
any exception had 4 toes. In the second cross (exp. 630) the 
Silky cock 446.1 had 5 toes on both feet. In F, of this cross we 
bred 8 chickens with 4—4, 10 with 5—5 toes. 
In the reciprocal cross (exp. 413) the Silky-hen 413.1 had double- 
 hallux. In F, 9 birds had a single, 4 a double hallux. Probably the 
Silky parent was heterozygous for this factor. 
The F9’s from birds with single hallux all bred true to this cha- 
racter. It behaved as a true recessive (vide tables 1 and 4). 
4. CONCLUSIONS. 
Mr. HouwiNK'’s reciprocal crosses of the Red Jungle Fowl 
(Gallus gallus) with the Silky Fowl did not give any confirmation 
to the theory of ,,Genasthenie” by A. v. TSCHERMAK, although the 
first results seemed to do so. The differences observed in the 
reciprocal offspring though they may not be explained in the way of 
sexlinked inheritance, do not show a regular paternal or maternal 
dominance. The segregation though not always passing away with the 
normal mendelian ratios, did also not show a reversion of these ratios. 
We think our experiments prove that cross breeding of „pure” 
breeds can bring many surprises, by the fact that dominating 
characters may be heterozygous even in breeds, bred true for a 
great number of generations. 
As to the heredity of the comb-form we cannot yet decide if the 
heterozygous state of the Silky cocks is a regular or incidental one. In 
the F; from Bankiva mother single combs and crown combs appeared, 
in the reciprocai cross (with Silky mother) we got only crowncombs. 
The single combs always bred true in F and Fs. the crown combs 
segregated and in their offspring several formsof rose comb appeared. 
Concerning the heredity of the other Silky-characters we could 
give some confirmation of former experiences, but we did not observe 
any sex-linked inheritance of the pigmentation of the skin. 
