1. Hybrids between blond male ring-doves and white female ring-doves are all blonds and they are mostly males. 2. The offspring of the reciprocal cross are about equally blonds or whites, but all of the white birds are females. Whiteness and the characters associated with it are sex-linked. Almost all of the blond birds are males. Male white birds appear, however, when white hybrid females are crossed back on white stock males. 3. The nestling hybrids are identical in appearance with the nestlings of the corresponding blond and white uncrossed ring-doves. 4. The phenomena observed are remarkably similar to those described by Durham and Marryat ('08) for canaries. 5. Sex-linked inheritance in birds and elsewhere also can be explained, in my judgment, more logically with the assumption that the male is heterozygous for sex and the female homozygous, than by the contrary hypothesis. 6. The appearance of recessive characters in F1 when the male parent is recessive may be explained with the assumption that the female determining gametes of the male parent may either possess or lack something which is responsible for the absence in female offspring of dominant characters carried by the female parent. 7. No evidence was obtained in support of the old idea that the first egg laid by doves produces a male. 8. Observations concerning the period of incubation and other points in the breeding habits of ring-doves are described.