No sooner can the young canaries eat alone, which happens on the thirteenth or fourteenth day, and sometimes even before they leave the nest, than the males begin to warble, and some females also, but in a less connected manner, which serves to point them out. As these pretty birds are so docile as to neglect entirely their natural song and imitate the harmony of our instruments, it is necessary immediately to separate from his companions and from every other bird the young one which is to be instructed, by putting him aside in a cage which is at first to be covered with a piece of linen, and afterwards with a darker cover. The air which is to be taught should be performed five or six times a day, especially in the evening and morning, either by whistling, or on a flageolet, or bird-organ; he will acquire it more or less readily, in from two to six months, according to his abilities and memory; if his separation from the other birds is delayed beyond the fourteenth day, he will retain some part of his father's song, which he will always intermingle with his acquired air, and consequently never perform it perfectly. The opinion of some, that the grayish canaries have more facility in learning than the yellow or the white, is unfounded, their only advantage over those of a different hue being that they are generally more robust and vigorous. I have not either found that the true No. 3 suits them better than No. 1 or No. 2; these latter, on the contrary, have appeared to me to please them best. There is too much trouble and risk in allowing canaries to go in and out of their cages for it to be worth the trouble of teaching them this. Notwithstanding all my attention, and the care which I have taken to follow exactly the prescribed rules, I have never succeeded; and the cleverest bird-fanciers have assured me that it should never be attempted but when they have young ones, and above all, there must be no canaries in the neighbouring houses, which might entice them away. Indeed it is no easy matter to accustom a bird to go and come. There, as in many other cases, conclusions in regard to the species have been drawn from individuals. It is certain that very few tame birds easily acquire this trick, and as I show in their histories, with respect to others, probabilities are too often stated as truths. DISEASES.--Birds which seldom enjoy the benefit of fresh and pure air, prisoners destitute in their confinement of the means of exercise, must be particularly subject to the common diseases which have been named, and also to many other peculiar ones. The following are some of the disorders incident to canaries.