406 C. H. DANFORTH 



an interpretation here would imply that the alcohol was without 

 effect on the transmission of Polydactyly. While this seems 

 to be the most probable conclusion, there are two points brought 

 out in table 4 that deserve attention. One of them is a phenom- 

 enon similar to that, mentioned in the discussion of brachy- 

 dactyly, namely, a positive correlation between the percentage 

 magnitudes of the A and C divisions of each experiment. In 

 1 are found the lowest values, in 2 intermediate values, and in 

 3 the highest values. This looks very much as if each of the 

 three males had his own peculiar capacity for producing poly- 

 dactyl offspring. 



The other point mentioned concerns experiment 3, where in 

 A the percentage of polydactyl chicks was 52 which is a most 

 unusual percentage in a cross of this sort. Here an effect of 

 the treatment seems to be indicated, and such a supposition 

 is strengthened by the fact that when the treatments were 

 stopped the percentage dropped to forty. It has been pointed 

 out that in the case of brachydactyly there is some evidence 

 that the amount of rise in the percentage is dependent upon the 

 strength of the treatment. It is possible that the same is true 

 of Polydactyly, but that the level required to produce results — 

 the threshold — is higher. Experiment 3-A, which had the highest 

 daily dosage and in which the treated male was most affected, 

 seems to have been the only one that was sufficiently rigorous 

 to produce an effect on the percentage to polydactyl chicks. 



For Polydactyly it may be said by way of conclusion that 

 the evidence is possibly negative, but that there is some indi- 

 cation that when the alcohol treatment of the heterozygous 

 parent is sufficiently intensive the relative number of poly- 

 dactyl young is increased. 



Color. In experiment 1 the female parents were homozy- 

 gous for the dominant white characteristic of the Leghorns, 

 while the treated male parent was a homozygous dark recessive. 

 Since each parent could produce only one kind of germ cell, 

 there was no chance for selection and the expectation of 100 

 per cent of white chicks was realized in the 217 individuals 

 whose color was determined. In the other three experiments 



