There has been much quibbling over the relative meanings of reversion and atavism. The general idea, whichever term we use, is that there is a "throwing back" in a noticeable degree through inheritance to some ancestral condition beyond the immediate parents. A few recent authors have taken the term atavism in a restricted sense and use it to signify specifically those not uncommon cases in which a particular character of an offspring resembles the corresponding character of a grandparent instead of a parent. Such, for example, as the blue eye-color of a child with brown-eyed parents, each of whom in turn has had a blue-eyed parent. The tendency of other authors is to abandon the term entirely because of the diversity of meaning that has been attached to it in the past. [Illustration: FIG. 1 Hybrid between the guinea-fowl and the common fowl, showing in many feathers reversion to a primitive chevron-like barring.] Certain classes of so-called reversions, such as the case of the eye-color just cited, are readily explicable on Mendelian principles as we shall see in a later chapter, but probably not all kinds of phenomena described as reversion can be so explained. For example, some seem to be cases of suppressed development. The word reversion, indeed, must be looked on as a convenient descriptive term rather than as the name of a single specific condition. =Telegony.--=There is yet a wide-spread belief in the supposed influence of an earlier sire on offspring born by the same mother to a later and different sire. This alleged phenomenon is termed _telegony_. For example, many dog-breeders assert that if a thoroughbred bitch has ever had pups by a mongrel father, her later offspring, although sired by a thoroughbred, will show taints of the former mongrel mating. In such cases the female is believed to be ruined for breeding purposes. Other supposed instances of such influences have been cited among horses, cattle, sheep, pigs, cats, birds, pets of various kinds and even men. The historic case most frequently quoted is that of Lord Morton's mare which bore a hybrid colt when bred to a quagga, a striped zebra-like animal now extinct. In later years the same mare bore two colts, sired by a black Arabian horse. Both colts showed stripes on the neck and other parts of the body, particularly on the legs. It was inferred that this striping was a sort of after effect of the earlier breeding with the quagga. In recent times, however, Professor Ewart has repeated the experiment a number of times with different mares using a Burchell zebra as the test sire. Although his experiments have been devised so as to conduce in every way possible to telegony his results have been negative. Moreover, it has been pointed out that the stripes on the legs of the two foals alleged to show telegony could not have been derived from the quagga sire for, unlike zebras, quaggas did not have their legs striped. Furthermore it is known that the