HOUWINK’S EXPER. CONC. THE ORIGIN OF SOME DOMESTIC ANIMALS 239 
b) that the most typical Sonnerat-character: waxy spots on the hack- 
les of the cock was almost absent in the F, birds, one F, cock only 
showing distinct, although very reduced, waxy-spots; while none 
of the others could attain more than simili-spots. 
Nor did this character reappear in any birds of successive ge- 
nerations, which (perhaps) is explained by the comparatively 
small number of them: 34 cocks in all, available for inspection. 
The most probable explanation is, that the reduced waxy spots 
are caused by but one chromosome of Sonnerat and that waxy 
spots not show plainly unless a pair of such chromosomes is 
present. In favor of this view, is the fact, that GHIGI, as the fig. 1 
of Pl. V shows, got very distinct waxy spots by backcrossing F, 
hybrids of Sonnerat and domestic poultry with Sonnerat-cocks. 
Insuch back crossed animals, GHIGI also obtained the typical Sonne- 
rat-breast of the hens, so that a pair of Sonnerat-chromosomes is pro- 
bably also necessary to produce that breast-pattern. (Pl. V fig. 2). 
The F, generation 
The hybrid cock 198.1 (Pl. IV fig. 1—2) was paired with each of his 
sisters. With 198.2 © he got three chicks in 1917: two cocks 206.1 4 
and 206.3 & and one hen 206.2 9. 
All three attained adult age: 206.3 4 however, born, as the others, on 
the 15th of April 1917, died already on the 3d of July 1918, while 206.2 2 
and 206.1 & became the parents of the F, generation: 391. 
Now two of these F, animals 206.1 4 and 206.3 $ are dead and stuf- 
fed, 206.2 © is alive. 
The same hybrid F, cock got with his other sister 198.3 © (very much 
like 198.2 ©) the F, 282. In 1917 but one chick, a male — afterwards 
numbered 282.18 3, was born; it died 13 Febr. 1919 when it was not 
much more than half grown and still had the strong crossbars charac- 
teristic of the primary plumage on the secondaries of the wing. 
In 1918 17 eggs of this cross were incubated, from which 8 chicks 
were hatched, while all the other eggs (9) contained full term chicks, 
so that fertilisation had been perfect and death in the egg was probably 
accidental. Notwithstanding the great food-difficulties of the wartime 
3 of the 8 chicks born were raised to adult age to wit: 
282.1 & born Aug.11 1918,sent to Mook Dec.1921,still alive March1923. 
