As the result of breeding thousands of moths Standfuss states that in no case observed by him has the female of a true hybrid been shown to be fertile. On the other hand, the occurrence of undoubted cases of fertility in male hybrids has been proved by crossing the male hybrids with the females of both parent species.
Ewart's Experiments with Crossing the Zebra and Horse, and the Wild Ass and A Burchell's zebra stallion, "Matopo," became the father of nine zebra hybrids by mares of various sizes and breeds. The hy brids exhibited a curious blending of charac ters, which seemed to have been derived partly from their actual and partly from their remote ancestors; some of the hybrids strongly suggest their zebra sire, others their respective dams, (but even the most zebra-like in form are utterly unlike their sire in their markings." He succeeded in securing a male wild ass (kiang) from central Asia and a couple of Mongolian pony mares, one a yellow dun and the other a chestnut. The wild ass was mated with the dun Mongol mare, a brownish-yellow Exmoor pony and a bay Shetland-Welsh pony. The kiang hybrid in its long legs, slender joints and speed took after its kiang parent. The mane and tail "are exactly what one would expect in a mule." This ki-tng hybrid also dif fers from the wild horse (Przewalsky's horse) in not neighing like a horse. The result is to prove that the wild horse is not a kiang-pony male, but a "good" species. Also in accordance with Mendel's law (see under HEREDITY) the kiang proved to be dominant, the Exmoor pony recessive. It is generally held that an old species is prepotent over a more recent variety.
Hybridity in The method of hy bridizing hermaphroditic flowers is to cut away their stamens before they are ripe and then enclose the flower in a paper bag. After the stigma has ripened the pollen is placed on it, the bag is again tied over the flower and not removed until the seed begins to form. Great advantages and improvements in agriculture have resulted from hybridizing plants, chief among which are many new varieties of culti vated plants, increased size and vigor, hardiness, or adaptation to warmer climates, and increased resistance to disease, as well as increase in odor of flowers and the quality and flavor of fruits.
Sterility in Thus far the cause of infertility in animals is unknown, but bot anists attribute the frequent sterility of plants to the imperfect formation of the pollen. Stand fuss' experiments with moths agree with Focke's statement as to the great variability of the off spring resulting from the crossing of a plant hybrid with one of the parent species. In plants, as discovered by Mendel, the proportion of the pure races is constantly increasing in the suc cessive generations descended from a hybrid.
Malformations and sports are much more fre especially in the floral organs in hybrids. than in individuals of a pure descent. Double flowers appear to be formed especially easily in hybrids. Recent experiments and results in the study of hybridity show how intimately the subject bears on heredity (q.v.) and the origin of species.
Bateson, William, 'Mendel's Principles of Heredity' (New York 1909) ; Dixey, F. A., 'Recent Experiments in Hybridization' (m Science Progress, Vol. VII, London 1898) ; Ewart, J. C., 'The Peny cuik Experiments' (ib. 1899) ; Ghigi, A., (Ricerche di Sistematica Sperimentale sul genere Gennmus Wagler' (Bologna 1909); de Vries, Hugo,