(3/25. Eudes-Deslongchamps 'Memoires de la Soc. Linn. de Normandie' volume 7 1842 page 41. Richardson 'Pigs, their Origin, etc.' 1847 page 30. Nathusius 'Die Racen des Schweines' 1863 s. 54.) As no wild pigs are known to have analogous appendages, we have at present no reason to suppose that their appearance is due to reversion; and if this be so, we are forced to admit that a somewhat complex, though apparently useless, structure may be suddenly developed without the aid of selection.
It is a remarkable fact that the boars of all domesticated breeds have much shorter tusks than wild boars. Many facts show that with many animals the state of the hair is much affected by exposure to, or protection from, climate; and as we see that the state of the hair and teeth are correlated in Turkish dogs (other analogous facts will be hereafter given), may we not venture to surmise that the reduction of the tusks in the domestic boar is related to his coat of bristles being diminished from living under shelter? On the other hand, as we shall immediately see, the tusks and bristles reappear with feral boars, which are no longer protected from the weather. It is not surprising that the tusks should be more affected than the other teeth; as parts developed to serve as secondary sexual characters are always liable to much variation.
It is a well-known fact that the young of wild European and Indian pigs (3/26. D. Johnson 'Sketches of Indian Field Sports' page 272. Mr. Crawfurd informs me that the same fact holds good with the wild pigs of the Malay peninsula.), for the first six months, are longitudinally banded with light-coloured stripes. This character generally disappears under domestication. The Turkish domestic pigs, however, have striped young, as have those of Westphalia, "whatever may be their hue" (3/27. For Turkish pigs see Desmarest 'Mammalogie' 1820 page 391. For those of Westphalia see Richardson 'Pigs, their Origin, etc.' 1847 page 41.); whether these latter pigs belong to the same curly-haired race as the Turkish swine, I do not know. The pigs which have run wild in Jamaica and the semi-feral pigs of New Granada, both those which are black and those which are black with a white band across the stomach, often extending over the back, have resumed this aboriginal character and produce longitudinally-striped young. This is likewise the case, at least occasionally, with the neglected pigs in the Zambesi settlement on the coast of Africa. (3/28. With respect to the several foregoing and following statements on feral pigs see Roulin in 'Mem. presentes par divers Savans a l'Acad.' etc. Paris tome 6 1835 page 326. It should be observed that his account does not apply to truly feral pigs; but to pigs long introduced into the country and living in a half- wild state. For the truly feral pigs of Jamaica see Gosse 'Sojourn in Jamaica' 1851 page 386; and Col Hamilton Smith in 'Nat. Library' volume 9 page 93. With respect to Africa see Livingstone 'Expedition to the Zambesi' 1865 page 153. The most precise statement with respect to the tusks of the West Indian feral boars is by P. Labat quoted by Roulin; but this author attributes the state of these pigs to descent from a domestic stock which he saw in Spain. Admiral Sulivan, R.N., had ample opportunities of observing the wild pigs on Eagle Islet in the Falklands; and he informs me that they resembled wild boars with bristly ridged backs and large tusks. The pigs which have run wild in the province of Buenos Ayres (Rengger 'Saugethiere' s. 331) have not reverted to the wild type. De Blainville 'Osteographie' page 132 refers to two skulls of domestic pigs sent from Patagonia by Al. d'Orbigny, and he states that they have the occipital elevation of the wild European boar, but that the head altogether is "plus courte et plus ramassee." He refers also to the skin of a feral pig from North America, and says "il ressemble tout a fait a un petit sanglier, mais il est presque tout noir, et peut-etre un peu plus ramasse dans ses formes."
The common belief that all domesticated animals, when they run wild, revert completely to the character of their parent-stock, is chiefly founded, as far as I can discover, on feral pigs.