The rivers nearest the deep water, such as those opening on the west coast of Ireland and on the Spanish and French shores of the Bay of Biscay, get their elvers “running up” as early as November, December, and January. The farther off the river the farther the elvers have to travel from the deep-sea nursery, so that in Denmark they don’t appear until May. Not the least curious part of the migration of the eel is the passage of the young elvers into the higher parts of rivers and remote streams. They are sometimes seen a hundred miles from the sea, actually wriggling in numbers up the face of a damp rock or wall ten or fifteen feet high, pushing one another from below upwards, so as to scale the obstacle and reach higher waters, like Japanese soldiers at a fort. I found them (so long ago that I hesitate to name the date—it was a year of cholera in London, followed by a great war) in a little rivulet which comes down the cliff at Ecclesbourne, near Hastings, close to a cottage frequented at that time by Douglas Jerrold. They were wriggling up in the damp grass and overflow of the driblet 150 feet above the shore, a stone’s throw below. They must have come out of the sea, attracted by the tiny thread of fresh water entering it at this spot.
The Danube and its tributary streams contain no eels, although the rivers which open into the Mediterranean are well stocked with them. This is supposed to be due to the fact that the Black Sea does not afford a suitable breeding-ground, and that the way through the Dardanelles is closed to eels by some natural law, as it has been to warships by treaty. Probably, however, it will be found that the geological changes in the area of sea and land are intimately connected with the migrations of the eel, and that the eel is originally a marine fish which did not in remote ages travel far from the deep waters. Its gradually acquired habit of running up fresh waters to feed has led it step by step into a frequentation of certain rivers which have become (by changes of land and sea) inconveniently remote from its ancestral haunts. An interesting question is whether at the not very distant period when there was continuous land joining England to France and the Thames and the Rhine had a common mouth opening into the North Sea, eels existed in the area drained by those two rivers; and, if so, by what route did they pass as silver eels to the deep sea, and by what route did the new generations of young eels hatched in the deep sea travel to the Thames and Rhine. It seems most probable that in those days there were no eels in the Thames and other North Sea rivers.
Our present knowledge of the romantic history of the common eel of our own rivers we owe in large part to the work done by the International Committee for the Investigation of the North Sea. Who would ever have imagined when he caught a wriggling eel, with a hook and worm thrown into a stagnant pool in the Midlands, that the muddy creature was some five or six years ago living as a glass-like leaf-shaped prodigy in the Atlantic depths, a hundred miles from Ireland? Who would have dreamed that it had come all that long journey by its own efforts, and would probably, if it had not been hooked, have wriggled one summer’s night out of the pond, across wet meadows, into a ditch, and so to the river, and back to the sea, and to the far-away orgy in the dark salt waters of the ocean-floor, to the consummation of its life and its strange, mysterious ending?
There are two points of interest to be mentioned in regard to the rivers Danube and Thames in connection with eels. I have trustworthy reports of the very rare occurrence of eels in streams connected with the Danube. Since the young elvers do not ascend the Danube, where do these rare specimens come from? There can be no doubt that they have made their way individually into the Danube “system” by migration through canals or ditches from tributaries of the Rhine or the Elbe. A similar explanation has to be offered of the eels which at present inhabit the Thames. I cannot find any evidence of the existence to-day of an “eel-fare”—that is, “a running up of elvers” in the river Thames. Probably about the same time as the foul poisoning of the Thames water by London sewage and chemical works put an end to the ascent of the salmon (about the year 1830), the entrance of the myriad swarm of young eels in their annual procession from the sea also ceased. The elvers were caught and made into fish-cakes in London before the nineteenth century, just as they are to-day at Gloucester. It would be interesting to know exactly when they ceased to appear in the Thames. A curious fact, however, is that young eels—not so small as “elvers,” but from three inches in length upwards—are taken close above London even to-day. Four years ago I obtained a number of this small size from Teddington. The question arises as to whether these specimens represent just a small number of elvers which have managed to swim through the foul water of London and emerge into the cleaner part of the river above. This is improbable. It is more likely that they have come into the Thames by travelling up other rivers such as the Avon—which are connected by cuttings with the Thames tributaries. But it certainly is remarkable that eels of only three inches in length—and therefore very young—should have managed to get not merely “into” the Thames (to the upper parts of which no doubt many thus travel and remain during growth), but actually “down” the Thames so far in the direction of its tidal water as is Teddington lock. The specimens from Teddington were placed by me in the Natural History Museum.
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MODERN HORSES AND THEIR ANCESTORS
The ever-increasing development of motor traffic leads to speculation as to what is to be in the immediate future the fate of the horse. What is its history in the past?
It is in nearly all cases a matter of great difficulty to trace the animals and plants which mankind has domesticated or cultivated to the original wild stock from which they have been derived. Lately we have gained new knowledge on the origin of the domesticated breeds of the horse. It is generally agreed that the Mongolian wild horse represents the chief stock from which the horses of Europe and those conveyed by Europeans to America were derived. This wild horse was formerly known as inhabiting the Kirghiz steppes, and was called the Tarpan. It became extinct there some seventy years ago. The natives of that district asserted that the pure breed was only to be met with farther East in the Gobi Desert of Central Asia. The Tarpan itself showed signs of mixed blood in having a mouse-coloured coat, which is a sure indication amongst horses of cross-breeding. Prevalsky, a Russian traveller, was the first to obtain specimens of the pure-bred wild horse of the Gobi Desert, which still exists. Live specimens have been brought to Europe, and some are in the possession of the Duke of Bedford. A female is mounted and exhibited in the Natural History Museum, and also a skeleton and skulls. Prevalsky’s horse, or the Mongolian wild horse, is of small stature, standing about twelve hands at the shoulder. The root of the tail is short-haired, the mane short and upright, without forelock. The body colour is yellow dun, the mane and tail black, as well as the lower part of the legs, and there is a dark stripe down the back. The muzzle in pure-bred specimens is white. The head is relatively large and the muzzle thick and relatively short. A very decided character is shown by the great size and relative length of the row of cheek-teeth, it being one-third larger than the same row of teeth in a Dartmoor pony of the same stature.