42 REPORT OF THE CONFERENCE ON GENETICS. 
sex, so that among the offspring of first crosses all the recessive are 
female. 
Rats: Grey colour is dominant over black, and colour over albino. 
“ Self-colour ’’ is partially dominant over piebald. The determinants for 
grey or black, and for “self’’ or piebald, may be borne by albino, so that an 
albino bearing “ self’? and grey, paired with a black piebald gives offspring 
which are grey and self-coloured. 
Hyprip Ducks BRED AND EXHIBITED BY J. L. BoNHOTE, 
M.A., F.L.8S., Hemet Hempstrap. 
One of the objects of these experiments has been to test the fertility 
of the hybrids of pure species, and it has been found that crosses between 
as many as five different species are all fertile. 
Two maim points may be noticed : 
(1) That the various crosses tend to split into two Hue marked forms, 
a light and a dark. 
(2) That the second and third generations become much lighter in 
coloration, and the drakes tend to lose their bright colours. 
Other points of interest are : 
(1) That resemblances are shown to the plumage of one parent in the 
winter dress, and to the other parent in the eclipse plumage. 
(2) That all variations seem to follow certain definite lines or tracts 
known as “ pecilomeres,”’ thereby showing resemblance to species other 
than their parents or to no known species. 
A résumé of an exhibition to the Zoological Society was laid on the 
table for those interested, and a full account will shortly appear in the 
Proceedings of the Fourth International Ornithological Congress. 
Pecilomeres have been dealt with in a paper to the Linnean Society 
(Proc. Linn. Soc. Zool. 1904, p. 95) and more fully in Knowledge (Dec. 
1905, Jan.—April 1906). 
SPECIMEN SHOWING RESULTS OF EXPERIMENTS ON HEREDITY IN 
PiGEoNS BY RICHARD STAPLES-BROWNE, CAMBRIDGE. 
Blue colour as found in Columba livia is shown in the F, generation, 
both in crosses between black and white birds, and also in the cross 
between a white fantail and a white tumbler. 
Serizs I. 
SKINS SHOWING RESULTS OF CROSSING WHITE FANTAIL AND 
WHITE TUMBLER. 
Tyre I.—Pure-bred white fantail. 
Type Il.—Pure-bred white twmbler.— The breeder of this bird has 
had a strain of white tumblers in his possession for twenty years. About 
fifteen years ago he introduced two white hens with red splashes, and 
since then has never used any but white birds, and only pure-white birds 
have been selected for stock. The strain occasionally throws birds 
showing coloured splashes, the coloured feathers being red, brown, or 
black. 
