As a general rule, however, close and in-and-in breeding should be carefully avoided where the race is not absolutely perfect, if it is desired to improve the breed; and as all the breeds of this kind of fowls are of mixed blood, the danger of such breeding is greater or less, in exact proportion as the distinctive characteristics are variant or fixed; and the danger still increases if the breed is composed of strains of blood greatly dissimilar, or of races widely differing in the conformation or general habits. _Preserving the distinctive breeds._ As to the time when the different breeds of hens should be separated in the spring, in order to preserve the breed pure, the most ample experience indicates that if the eggs be preserved and set after a separation of _two days_, the breed will be perfect, the offspring having all the characteristics or distinctive marks. When a valuable breed is produced, either by accident or design, it should be preserved, and the subsequent breeding should continue from that stock; otherwise, there is no certainty of the purity of the blood of the new breed, for it does not follow that a different parentage, though of the same name or original breed precisely, will produce the same new breed, or any thing resembling it. The Dorking fowl, for instance, was originally produced by crossing the Great Malay with the English Game, as an accident; but it by no means follows that Dorkings are the uniform, or even the common result of such a cross, for hundreds of similar experiments have proved unsuccessful. The breeding, therefore, to be pure-blooded, must continue from the stock originally produced by accident; and as such breeding produces the leading characteristics of the race with great uniformity, the genuineness of the breed cannot be doubted. In order to produce a good cross, the parentage should be healthy, and from healthy races, not materially dissimilar in their general habits. The _size of the leg_ should always be looked to, in order to judge accurately as to purity of blood. If the leg is large for the breed--that is, if larger than the generality of the same breed--the purity of the blood, the fineness of the flesh, and most of the other valuable qualities, can be relied on; but, if the legs are smaller than most others of the same breed, the fowl is spurious, and of deteriorated blood. The fifth toe and feathered legs of some breeds were originally the result of accident; but by long and careful breeding, they have become incorporated into the nature of certain races of general, though not universal or essential, requisites. When a fowl exhibits any special marks indicative of all the races or breeds from which the cross originated, it is a sure evidence of extraordinary purity of blood, and of the superior excellence of the race. The best fowls of the race should always be selected for crossing or general breeding; otherwise the breeds will degenerate.