Genetic studies in poultry. VII. Notes on polydactyly

Conclusion

In conclusion we may add a few words on the impression which we have gathered from the available evidence as to the genetical nature of polydactyly in. the fowl. In the first place we feel little doubt that there is a definite factor for polydactyly. It is evident also that this factor can be carried by an apparently normal 4-toed bird. This is probably due to the existence of a factor (or possibly factors) inhibiting the action of the factor for polydactyly, and this factor (or factors) may be carried by normal recessive 4-toed birds. Further, since the evidence points to polydactylous birds being also capable of carrying the inhibitor, we must suppose that we are also concerned with some other factor, or factors, rendering possible the manifestation of the polydactylous effect in spite of the presence of the inhibitor. But although we have devised various schemes along these lines we have not found one which we consider satisfactory. Our failure, however, has been due more to lack of necessary data than to antagonistic facts. Where the gaps in the evidence are so large there are so many possible interpretations that we do not consider further efforts in this direction to be at present profitable. We agree with Dunn that “it is useless at present to frame more complex hypotheses since the data in a form wherewith to test them do not yet exist.” Yet through the tangle of facts we so often catch glimpses of apparent order that we feel confident that the solution, when it comes, will be found relatively simple.