20 PRINCIPLES OF BREEDING 



As white with black points is a combination of colour 

 unknown in either of the pure breeds from which the cattle 

 sprang, its repeated appearances can best be explained as 

 instances of reversion to an early ancestor. 



Atavism may occur in two classes (i.) In Pure-bred 

 Stock. (2.) In Cross-bred Stock. 



1st. Reversion in Pure Breeds (caused by an innate 

 latent tendency). The aboriginal species of domestic cattle 

 and sheep no doubt had horns for defence and attack ; now 

 many are without them, though they yet exist in the cases of 

 most mountain breeds of sheep at home and abroad. Some- 

 times a ram of a polled breed, such as the Cheviot, develops 

 horns. In cattle this is also the case, as imperfectly formed 

 horns at times appear in White, Red, and Black Polls. Sheep, 

 for their better protection when wild, were, it is believed, 

 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, such as 

 strong coarse wool (although there are very striking excep- 

 tions), that it has become proverbial to describe the un- 

 fortunate member of a family as the "black sheep." Till 

 recently it has been the scientific rule to consider reversion 

 due to "latent ancestral units," but, as strongly urged by 

 Reid, "it is infinitely more probable that it is due to incom- 

 plete recapitulation." 



2nd. Reversion in Cross Animals ("untrue or false 

 atavism "). This is much more common. De Vries has 

 named it Vicinisin in the botanical world, from vicinus, 

 neighbour, "to indicate the sporting of a variety under the 

 influence of others in its vicinity." When two distinct, 

 improved 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 genera- 

 tions. The young often assume the colour of one parent, 

 and in time change it for that of the other. The calf from a 

 black cow by a red bull is often born red or brown, becoming 

 black afterwards ; 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 (see 



