The Cut-throat Finch (_Amadina fasciata_) and Red-headed Finch (_A. erythrocephala_) of Africa have hybridised in aviaries, and the produce has proved fertile. The red-headed finch, among other differences, is far larger than the cut-throat, and the males have the head all red, not merely a throat-band of that colour. The Japanese Greenfinch (_Ligurinus sinicus_) which is not green, but brown and grey, with bolder yellow wing- and tail-markings than our larger European greenfinch, has produced fertile hybrids with this latter bird. [Illustration: MALE AMHERST PHEASANT] The Red Dove of India (_Oenopopilia tranquebarica_) has produced hybrids with the tame Collared Dove (_T. risorius_) and these have bred again when paired with the red species. _O. tranquebarica_, although presenting a general similarity to the collared dove, is truly distinct, being much smaller, with a shorter tail, and displaying a marked sex-difference (the male only being red, and the female drab). Its voice is also utterly unlike the well-known penetrating and musical _coo_ of the Collared Dove. There is a large class of fertile wild hybrids produced between forms differing only in colour, such as those between the Hooded Crow (_Corvus cornix_) and Carrion Crow (_Corvus corone_), the various species of _Molpastes_ bulbuls, and the Indian Roller (_Coracias indica_) and Burmese Roller (_C. affinis_). Indeed, it may be said that wherever two such colour-species meet they hybridize and become more or less fused. In this connection sportsmen, as mentioned by Darwin, performed unconsciously a most interesting experiment when, more than a century ago, they introduced largely into their coverts the Chinese Ring-necked Pheasant (_Phasianus torquatus_) and the Japanese _P. versicolor_. So freely has the former bred with the common species already present there (_Phasianus colchicus_) that nowadays nearly all our English pheasants show traces of the cross in the shape of white feathers on the neck, or the green tinge of the plumage of the lower back. The influence of the Japanese Green Pheasant (_P. versicolor_) has been very slight. It is, of course, open to anyone to assert that such crosses are not true hybrids, as the species are not fully distinct, but mere colour-mutations. The fact of the intermingling, however, is a fatal blow to the theory of recognition marks, since it demonstrates that merely distinctive colouring is not a preventative of cross-breeding. To this matter we shall return later. Fertile Hybrids among Amphibia