That a variation strongly developed in both parents is apt to be augmented in the offspring is commonly believed by breeders. Darwin was assured that to get a good jonquil-coloured canary it does not answer to pair two jonquils, as the colour then comes out too strong, or is even brown. Moreover,[DT] "if two crested canaries are paired, the young birds rarely inherit this character; for in crested birds a narrow space of bare skin is left on the back of the head, where the feathers are upturned to form the crest, and, when both parents are thus characterized, the bareness becomes excessive, and the crest itself fails to be developed." On the whole, it would seem that variations may either be neutralized or augmented in inheritance; but the determining causes are not well understood. Another fact to be noticed with regard to the inheritance of variations is that some characters blend in the offspring, while others apparently fail to do so. Mr. Francis Galton,[DU] speaking of human characters, gives the colour of the skin as an instance of the former, that of the eyes as an example of the latter. If a negro marries a white woman, the offspring are mulattoes. But the children of a light-eyed father and a dark-eyed mother are either light-eyed or dark-eyed. Their eyes do not present a blended tint. Among animals the colour of the hair or feathers is often a mean or blended tint; but not always. Darwin gives the case of the pairing of grey and white mice, the offspring of which are not whitish-grey, but piebald. If you cross a white and a black game bird, the offspring are either black or white, neither grey nor piebald. Sir R. Heron crossed white, black, brown, and fawn-coloured Angora rabbits, and never once got these colours mingled in the same animal, but often all four colours in the same litter. He also crossed "solid-hoofed" and ordinary pigs. The offspring did not possess all four hoofs in an intermediate condition; but two feet were furnished with properly divided and two with united hoofs.[DV] Professor Eimer[DW] has noticed that, in the crossing of striped and unstriped varieties of the garden snail, _Helix hortensis_, the offspring are either striped or unstriped, not in an intermediate or faintly striped condition.