抄録
In the former paper (Yamashina '41), the author reported the results of cytological investigations on sterility of hybrids between the Muscovy duck _??_ (Cairina moschata) and the Domestic duck _??_ (Anas platyrhyncha var. domestica). The present study deals with the cytology of the hybrids out of the reciprocal mating, Domestic duck _??_×Muscovy duck _??_. In this experiment, it was found that the hybrid offsprings of this cross posses well developed genital organs in both sexes, though they are completely infecund. Dissimilar to the former case, noticeable is that in the F1 females from this cross there was an ovary of normal structure and an oviduct of normal size, and that they laid eggs which were much smaller than those of either of the parent birds.
