India in 1887 as seen by Robert Wallace / [Robert Wallace].

  • Robert Wallace
Date:
1888
Catalogue details

Licence: Public Domain Mark

Credit: India in 1887 as seen by Robert Wallace / [Robert Wallace]. Source: Wellcome Collection.

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    new vigour. This explains the success of crossing mongrel cows with a pure shorthorn hull. Atavism, or “throwing hack,” or “reversion,” is the reacquiring hy an animal of some character which the immediate parents had not, hut which existed in its ancestors. Two classes—(1.) In Purebred Stock. (2.) In Cross Stock. 1st, Reversion in Pure Breeds.—The aboriginal species of domestic cattle and sheep no doubt had horns for defence and attack ; now many are without them. Sometimes, however, a ram of a j>olled breed, as the Cheviot, has small horns. In cattle this is also the case, as imperfectly formed horns at times appear in both Reel Polls and Galloways. Sheep, for their better protection when wild, were originally brown or dingy black. Now and then in the best flocks reversion is shown by the appearance of a black sheep ; and so frequently is this correlated with poor quality, that it has become proverbial to describe the unfoitunate member of a family as the “ black sheep.” 2nd, Reversion in Cross Animals.—This is much more common. When two distinct breeds are crossed, the offspring has a strong tendency to revert to one of the pure forms, or rather to an inferior ancestor of one of them ; and this lasts for generations. The young often take the colour of one parent, and in time change it for the other. The calf from a black cow by a red bull is often born red, becoming black after- wards ; and the mouse-coloured foal of a chestnut mare may become chestnut. “ The act of crossing in itself gives an impulse towards reversion,” as seen by characters appearing in the young that had not been seen in either pure breed for generations. Calves are sometimes produced white with dark ears, like the ancient wild cattle, by a red shorthorn bull on West Highland cows. Cross-breds are often wilder than pure-breds. This is noticed particularly in cattle and sheep. Cross sheep are not so easily fenced, and a dairy of cross cows is much more difficult to train to stand for milking in the field than pure shorthorns. Domestication increases the fertility of animals, if properly bred and not overfed. Being in an improving condition at the time of con- ception increases the number of twins. In a Hock of ewes the largest number of twins is got the first few days the ram is out. The first young of most animals run slightly more to the female than to the male side. Barrenness or uncertainty may be caused by, 1st, Over-feeding in the case of either sex. thus loading the reproductive organs with fat.