Goodale’s results with females (ducks) are not so clear cut, because the ovariotomized females turned out to be of two sorts. One sort is almost identical with the male, the other is more intermediate. There are sufficient reasons for thinking, he says, that these differences are not due to defective operations. Goodale suggests a genetic difference in the females used, but this is apparently even to Goodale himself not a very satisfactory solution. For our present purpose the important fact is that the ovariotomized female may assume the perfect male plumage. Evidently the ovary produces some substance which, as in the hen, suppresses the potential plumage of the male. One such female known to have had all the ovary removed never assumed the summer (eclipse) plumage of the drake. On the other hand, another female developed first the nuptial plumage, but this was replaced by the summer coat “of the male of this variety.” Again, in the summers of 1914 and 1915 the change to the eclipse plumage was followed in the autumn by a return to the nuptial plumage. How can we explain the apparent discrepancy of Goodale’s results? In one case, the nuptial plumage was molted to nuptial plumage; in the other case an eclipse plumage appeared at the breeding-season. Goodale regards the latter case as a more perfect approach to the male than the former, but this view undoubtedly offers serious theoretical difficulties. It seems to me possible to suppose that in those cases where the summer plumage appeared there was in reality enough ovarian tissue (or related tissue) left after the operation to produce an effect at the normal season for such ovarian tissue to become most active. It might then suffice to eclipse the male plumage sufficiently to make it very similar to the eclipse of the normal male. At any rate, on this basis we have a consistent explanation of the entire complex of phenomena.