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Dt D. FÉNYES 
hybrid of the first generation is % grey + % white blended ; all the hybrids 
are whole-coloured greys, still they are not precisely like the pure-bred 
greys, their colour being of a slightly lighter shade, or, if not lighter, with 
slight white markings. The inter se matings of these hybrids result, on the 
average, 8 all-grey : 1 all-white hybrids in the second generation. — The pe¬ 
digree ratio of the cross white x black is 1: 2: 1 on the average. Each hybrid 
of the first generation is % white -f- y 2 grey -f- % black blended; all the 
hybrids are whole-coloured greys, still they are not exactly like the pure¬ 
bred greys, their colour varying from a slightly lighter to a slightly darker 
shade, or, if not generally lighter or darker, with slight white and black 
markings. The inter se matings of these hybrids result, on the average, 
1 all-white : 2 all-grey : 1 all-black hybrids, in the second generation. 
Sexual ratio. — First example. White pure breed and black pure 
breed are descended from the grey pure breed. Suppose, that, in the grey 
breed there are, on the average, 1 male, in the white, 2 males, and 
in the black breed, 3 males to each female. When white and black are 
crossed, 
grey (1 c?:l?) 
grey (1 <J: 1 ■?) 
J 
black (3 SS • 1 ?) 
Ï 
white (2 SS : 1 $) X 
7 males : 4 females can be reckoned on. — Second example. A man who has 
brothers only, but no sister, marries a woman who has as many brothers 
as sisters, including herself. From this marriage there will issue, in all pro¬ 
bability, three times as many boys as girls. When, in another case, a man 
who has brothers only, but no sister, will marry a woman who likewise 
has only brothers, this marriage will produce, in all probability, only boys. 
The probability, which can be estimated beforehand, will be the more 
approached in fact by the sexual rate of the children who will be born, 
when not only the sexual rate of the brothers and sisters of the pa¬ 
rents, but also that of the more remote ancestors, and that of the 
collateral lines, are also taken into account. The families of our relations 
and acquaintances supply us with numerous examples to prove the 
correctness — or not — of the simple method made known here, which 
method, if correct, would become important just from the standpoint of 
making up the deficiency for loss of life in consequence of the war, 
viz., of increasing the population, and of regulating the sexual ratio. — 
Third example. I found, that some of my fox terrier sires produced, 
out of the bitches of the same strain, many times more bitch than dog- 
puppies. The same dogs sired, on the other hand, ex such bitches of other 
strains, which had more full-sisters than brothers, nearly as many dog as 
