Charles Davenport

“ Abundant statistics give a clear answer. In the first place, the progeny of two Y-combed F1 parents is found to show the following distribution of comb types: Y comb 471, or 47.3 per cent; I comb 289, or 29.0 per cent; oo comb 226, or 22.7 per cent; and no comb 10, or 1 per cent. The presence of no comb in F2 speaks for the second hypothesis, but instead of the 6.25 per cent combless expected on that hypothesis only 1 per cent appears. There is no close accord with expectation on the second hypothesis. ”

“ Moreover, agreement with the second hypothesis is fairly close, for that calls for 3 families with combless children and there were actually 3 such families showing a total of 1.8 per cent combless, where expectation is 2.8 per cent. What is opposed to any hypothesis is the appearance of some Y-combed offspring; and to account for this the hypothesis is suggested that the germ-cells of some parents with oo comb contain traces of the I-comb determiner. ”

“ It is a consequence of this second hypothesis that, in F2, of every 16 young 9 should have the Y comb; 3 the I comb; 3 the oo comb, and I no comb at all. It follows further that the progeny of two F2 parents will differ in different families. Thus if a Y-combed bird of type a be mated with a bird of any type, all of the progeny will have the Y comb. ”