Hybridological experiment in the genus Cygnus Bechstein: Cygnus melanocoryphus x C.olor F₁ hybrids. Cases of hybridization among different subspecies and also species of genus Cygnus occur rather frequently especially in Zoological Gardens. However, no indication are reported on the crossbreed between the two species: Cygnus melanocoryphus and C.olor. Some of these F₁ hybrids were obtained at the Zoo of Turin in 1969 and later on sent to be studied to the University Zooculture Institute in Pisa. The somatic features of these hybrids have been described in the following way: the melanocoryphus x olor hybrids recall on the whole this last species, that is the one which acted as mother, though the facial glabrous space, the nose-frontal tubercle, the beak and the claws show a slight change in colour.