recovered the proper color of its fur in rather less than four years.” Another striking case of sudden variation is found in the peacock. It is all the more remarkable because this bird has hardly varied at all under domestication, and is almost exactly like the wild species living in India to-day. Darwin states: “There is one strange fact with respect to the peacock, namely, the occasional appearance in England of the ‘japanned’ or ‘black-shouldered’ kind. This form has lately been named, on the high authority of Mr. Slater, as a distinct species, viz. _Pavo nigripennis_, which he believes will hereafter be found wild in some country, but not in India, where it is certainly unknown. The males of these japanned birds differ conspicuously from the common peacock in the color of their secondary wing-feathers, scapulars, wing-coverts, and thighs, and are, I think, more beautiful; they are rather smaller than the common sort, and are always beaten by them in their battles, as I hear from the Hon. A. S. G. Canning. The females are much paler-colored than those of the common kind. Both sexes, as Mr. Canning informs me, are white when they leave the egg, and they differ from the young of the white variety only in having a peculiar pinkish tinge on their wings. These japanned birds, though appearing suddenly in flocks of the common kind, propagate their kind quite truly.” In two cases, in which these birds had appeared quite suddenly in flocks of the ordinary kind, it is recorded that “though a smaller and weaker bird, it increased to the extinction of the previously existing breed.” Here we have certainly a remarkable case of a new species suddenly appearing and replacing the ordinary form, although the birds are smaller, and _are beaten in their battles_. Darwin has given an admirably clear statement of his opinion as to the _causes of variability_ in the opening paragraph of his chapter dealing with this topic in his “Animals and Plants.” Some authors, he says, “look at variability as a necessary contingent on reproduction, and as much an original law as growth or inheritance. Others have of late encouraged, perhaps unintentionally, this view by speaking of inheritance and variability as equal and antagonistic principles. Pallas maintained, and he has had some followers, that variability depends exclusively on the crossing of primordially distinct forms. Other authors attribute variability to an excess of food, and with animals, to an excess relatively to the amount of exercise taken, or again, to the effects of a more genial climate. That these causes are all effective is highly probable. But we must, I think, take a broader view, and conclude that organic beings, when subjected during several generations to any change whatever in their condition, tend to vary; the kind of variation which ensues depending in most cases in a far higher degree on the nature of the constitution of the being, than on the nature of the changed conditions.”