Partial infertiliyt of intergeneric hybrid eggs between the muscovy drake and the common duck

1. The female Common ducks were artificially inseminated: in one series of experiments the semen of its own breed was used; and in the other, the semen of the Muscovy drake was used.
2. Both in homo- and heteroinsemination, the maximum fertility rate was obtained on the second day following the insemination: 80% in the former and 75% in the latter. On the third day, the fertility rate went down to 50% in both cases.
3. The maximum length of time during which the semen remained capable of fertilizing was likewise 7 days in both the species.
4. There is a marked difference, however, in the fertility resulted during the whole week following the insemination, between the heterologous semen and the homologous semen: the fertility rate in the former being 27.6% and in the latter 33.3%.
5. The partial infertility of the Muscovy drake in producing the mule-duck is thus experimentally proved.
6. It seems to be unjustified to ascribe this partial infertility to the copulatory hindrance caused by the differences in mating habits of the two duck species, because the fertility rate in the hybrid eggs could not be raised even with artificial insemination.
7. The testicular activity shown by the total number of sperms per ejaculate of the Muscovy throughout the year is strikingly low compared with that of the Common duck. This suggests that the Muscovy duck, though domesticated prior to the importation to Europe, has not yet so much changed in its breeding habit as the Common duck which acquired habits of polygamy and of breeding all the year.
8. For the purpose of increasing the fertility rate of hybrid eggs, in artificial insemination too high a dilution of the Muscovy's semen should be avoided and an adequate dilutor for the duck should be newly devised.