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05 - Laws of Variation 05-12 - Reversion to Long Lost Characters 10 No doubt it is a very surprising fact that characters should reappear after having been lost for many, probably for hundreds of generations.

But when a breed has been crossed only once by some other breed, the offspring occasionally show for many generations a tendency to revert in character to the foreign breed- some say, for a dozen or even a score of generations.

After twelve generations, the proportion of blood, to use a common expression, from one ancestor, is only 1 in 2048;
and yet, as we see, it is generally believed that a tendency to reversion is retained by this remnant of foreign blood.

In a breed which has not been crossed, but in which both parents have lost some character which their progenitor possessed, the tendency, whether strong or weak, to reproduce the lost character might, as was formerly remarked, for all that we can see to the contrary, be transmitted for almost any number of generations.

When a character which has been lost in a breed, reappears after a great number of generations, the most probable hypothesis is, not that one individual suddenly takes after an ancestor removed by some hundred generations, but that in each successive generation the character in question has been lying latent, and at last, under unknown favourable conditions, is developed.

With the barb-pigeon, for instance, which very rarely produces a blue bird, it is probable that there is a latent tendency in each generation to produce blue plumage.

Barb Pigeon
Barb Pigeon


The abstract improbability of such a tendency being transmitted through a vast number of generations, is not greater than that of quite useless or rudimentary organs being similarly transmitted. A mere tendency to produce a rudiment is indeed sometimes thus inherited.
05 - Laws of Variation 05-12 - Reversion to Long Lost Characters 20 As all the species of the same genus are supposed to be descended from a common progenitor, it might be expected that they would occasionally vary in an analogous manner; so that the varieties of two or more species would resemble each other, or that a variety of one species would resemble in certain characters another and distinct species,- this other species being, according to our view, only a well marked and permanent variety.

But characters exclusively due to analogous variation would probably be of an unimportant nature, for the preservation of all functionally important characters will have been determined through natural selection, in accordance with the different habits of the species.

It might further be expected that the species of the same genus would occasionally exhibit reversions to long lost characters.

As, however, we do not know the common ancestors of any natural group, we cannot distinguish between reversionary and analogous characters.

If, for instance, we did not know that the parent rock-pigeon was not feather-footed or turn-crowned, we could not have told, whether such characters in our domestic breeds were reversions or only analogous variations; but we might have inferred that the blue colour was a case of reversion from the number of the markings, which are correlated with this tint, and which would not probably have all appeared together from simple variation.

Rock Pigeon
Rock Pigeon


More especially we might have inferred this, from the blue colour and the several marks so often appearing when differently coloured breeds are crossed.

Hence, although under nature it must generally be left doubtful, what cases are reversions to formerly existing characters, and what are new but analogous variations, yet we ought, on our theory, sometimes to find the varying offspring of a species assuming characters which are already present in other members of the same group.

And this undoubtedly is the case. The difficulty in distinguishing variable species is largely due to the varieties mocking, as it were, other species of the same genus.
05 - Laws of Variation 05-12 - Reversion to Long Lost Characters 30 A considerable catalogue, also, could be given of forms intermediate between two other forms, which themselves can only doubtfully be ranked as species; and this shows, unless all these closely allied forms be considered as independently created species, that they have in varying assumed some of the characters of the others.

But the best evidence of analogous variations is afforded by parts or organs which are generally constant in character, but which occasionally vary so as to resemble, in some degree, the same part or organ in an allied species.

I have collected a long list of such cases; but here, as before, I lie under the great disadvantage of not being able to give them.

I can only repeat that such cases certainly occur, and seem to me very remarkable.
05 - Laws of Variation 05-12 - Reversion to Long Lost Characters 40 I will, however, give one curious and complex case, not indeed as affecting any important character, but from occurring in several species of the same genus, partly under domestication and partly under nature. It is a case almost certainly of reversion.

The ass sometimes has very distinct transverse bars on its legs, like those on the legs of the zebra: it has been asserted that these are plainest in the foal, and, from inquiries which I have made, I believe this to be true.

ass
ass

zebra
zebra


The stripe on the shoulder is sometimes double, and is very variable in length and outline.

A white ass, but not an albino, has been described without either spinal or shoulder stripe: and these stripes are sometimes very obscure, or actually quite lost, in dark-coloured asses.

The koulan of Pallas is said to have been seen with a double shoulder-stripe. Mr. Blyth has seen a specimen of the hemionus with a distinct shoulder-stripe, though it properly has none; and I have been informed by Colonel Poole that the foals of this species are generally striped on the legs, and faintly on the shoulder. The quagga, though so plainly barred like a zebra over the body, is without bars on the legs; but Dr. Gray has figured one specimen with very distinct zebra-like bars on the hocks.

koulan
koulan

quagga
quagga
05 - Laws of Variation 05-12 - Reversion to Long Lost Characters 50 With respect to the horse, I have collected cases in England of the spinal stripe in horses of the most distinct breeds, and of all colours: transverse bars on the legs are not rare in duns, mouse-duns, and in one instance in a chestnut a faint shoulder-stripe may sometimes be seen in duns, and I have seen a trace in a bay horse.

horse
horse

England
England


My son made a careful examination and sketch for me of a dun Belgian cart-horse with a double stripe on each shoulder and with leg-stripes; I have myself seen a dun Devonshire pony, and a small dun Welsh pony has been carefully described to me, both with three parallel stripes on each shoulder.

Belgian Cart Horse
Belgian Cart Horse

Welsh Pony
Welsh Pony
05 - Laws of Variation 05-12 - Reversion to Long Lost Characters 60 In the north-west part of India the kattywar breed of horses is so generally striped, that, as I hear from Colonel Poole, who examined this breed for the Indian Government, a horse without stripes is not considered as purely-bred.

India
India

Kathiwari Horse
Kathiwari Horse


The spine is always striped; the legs are generally barred; and the shoulder-stripe, which is sometimes double and sometimes treble, is common; the side of the face, moreover, is sometimes striped.

The stripes are often plainest in the foal; and sometimes quite disappear in old horses.

Colonel Poole has seen both gray and bay kattywar horses striped when first foaled. I have also reason to suspect, from information given me by Mr. W. W. Edwards, that with the English race-horse the spinal stripe is much commoner in the foal than in the fullgrown animal.
Race Horse
Race Horse


I have myself recently bred a foal from a bay mare (offspring of a Turkoman horse and a Flemish mare) by a bay English race-horse; this foal when a week old was marked on its hinder quarters and on its forehead with numerous, very narrow, dark, zebra-like bars, and its legs were feebly striped: all the stripes soon disappeared completely.

Turkoman Horse
Turkoman Horse


Without here entering on further details, I may state that I have collected cases of leg and shoulder stripes in horses of very different breeds in various countries from Britain to eastern China; and from Norway in the north to the Malay Archipelago in the south. In all parts of the world these stripes occur far oftenest in duns and mouse-duns; by the term dun a large range of colour is included, from one between brown and black to a close approach to
cream-colour.

horses
horses

England
England

China
China

Norway
Norway

Malayan archipelago
Malayan archipelago
05 - Laws of Variation 05-12 - Reversion to Long Lost Characters 70 I am aware that Colonel Hamilton Smith, who has written on this subject, believes that the several breeds of the horse are descended from several aboriginal species- one of which, the dun, was striped; and that the above described appearances are an due to ancient crosses with the dun stock.

Dun Horse
Dun Horse


But this view may be safely rejected; for it is highly improbable that the heavy Belgian cart-horse, Welsh ponies, Norwegian cobs, the lanky kattywar race, &c., inhabiting the most distant parts of the world, should all have been crossed with one supposed aboriginal stock.

Belgian Cart Horse
Belgian Cart Horse

Welsh Pony
Welsh Pony

Kathiwari Horse
Kathiwari Horse
05 - Laws of Variation 05-12 - Reversion to Long Lost Characters 80 Now let us turn to the effects of crossing the several species of the horse-genus.

Rollin asserts, that the common mule from the ass and horse is particularly apt to have bars on its legs; according to Mr. Gosse, in certain parts of the United States about nine out of ten mules have striped legs.

mule
mule

ass
ass

horse
horse

Philip Henry Gosse
Philip Henry Gosse

United States
United States


I once saw a mule with its legs so much striped that any one might have thought that it was a hybrid-zebra; and Mr. W. C. Martin, in his excellent treatise on the horse, has given a figure of a similar mule.

zebra
zebra


In four coloured drawings, which I have seen, of hybrids between the ass and zebra, the legs were much more plainly barred than the rest of the body; and in one of them there was a double shoulder-stripe.

In Lord Morton's famous hybrid, from a chestnut mare and male quagga, the hybrid, and even the pure offspring subsequently produced from the same mare by a black Arabian sire, were much more plainly barred across the legs than is even the pure quagga.

quagga
quagga

Arabian Horse
Arabian Horse

quagga
quagga


Lastly, and this is another most remarkable case, a hybrid has been figured by Dr. Gray (and he informs me that he knows of a second case) from the ass and the hemionus; and this hybrid, though the ass only occasionally has stripes on its legs and the hemionus has none and has not even a shoulder-stripe, nevertheless had all four legs barred, and had three short shoulder-stripes, like those on the dun Devonshire and Welsh ponies, and even had some zebra-like stripes on the sides of its face.

ass
ass

hemionus
hemionus

Dun Horse
Dun Horse

Welsh Pony
Welsh Pony

zebra
zebra


With respect to this last fact, I was so convinced that not even a stripe of colour appears from what is commonly called chance, that I was led solely from the occurrence of the face-stripes on this hybrid from the ass and hemionus to ask Colonel Poole whether such face-stripes ever occurred in the eminently striped kattywar breed of horses, and was, as we have seen, answered in the affirmative.
05 - Laws of Variation 05-12 - Reversion to Long Lost Characters 90 What now are we to say to these several facts?

We see several distinct species of the horse-genus becoming, by simple variation, striped on the legs like a zebra, or striped on the shoulders like an ass. In the horse we see this tendency strong whenever a dun tint appears- a tint which approaches to that of the general colouring of the other species of the genus.

horse
horse

ass
ass

Dun Horse
Dun Horse


The appearance of the stripes is not accompanied by any change of form or by any other new character.

We see this tendency to become striped most strongly displayed in hybrids from between several of the most distinct species.

Now observe the case of the several breeds of pigeons: they are descended from a pigeon (including two or three sub-species or geographical races) of bluish colour, with certain bars and other marks; and when any breed assumes by simple variation a bluish tint, these bars and other marks invariably reappear; but without any other change of form or character.

pigeon
pigeon


When the oldest and truest breeds of various colours are crossed, we see a strong tendency for the blue tint and bars and marks to reappear in the mongrels.

I have stated that the most probable hypothesis to account for the reappearance of very ancient characters, is- that there is a tendency in the young of each successive generation to produce the long-lost character, and that this tendency, from unknown causes, sometimes prevails.

And we have just seen that in several species of the horse-genus the stripes are either plainer or appear more commonly in the young than in the old.

Call the breeds of pigeons, some of which have bred true for centuries, species; and how exactly parallel is the case with that of the species of the horse-genus!

horse
horse

pigeon
pigeon


For myself, I venture confidently to look back thousands on thousands of generations, and I see an animal striped like a zebra, but perhaps otherwise very differently constructed, the common parent of our domestic horse (whether or not it be descended from one or more wild stocks), of the ass, the hemionus, quagga, and zebra.

horse
horse

ass
ass

hemionus
hemionus

quagga
quagga

zebra
zebra
05 - Laws of Variation 05-12 - Reversion to Long Lost Characters 100 He who believes that each equine species was independently created, will, I presume, assert that each species has been created with a tendency to vary, both under nature and under domestication, in this particular manner, so as often to become striped like the other species of the genus; and that each has been created with a strong tendency, when crossed with species inhabiting distant quarters of the world, to produce hybrids resembling in their stripes, not their own parents, but other species of the genus.

To admit this view is, as it seems to me, to reject a real for an unreal, or at least for an unknown, cause. It makes the works of God a mere mockery and deception; I would almost as soon believe, with the old and ignorant cosmogonists, that fossil shells had never lived, but had been created in stone so as to mock the shells living on the seashore.
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