in England) distinguish “yellow eels” and “silver eels” (see Plate I.
opposite title page). We used to distinguish also snigs and grigs, or
narrow-nosed and broad-nosed eels (probably males and females). The
remarkable fact, admitted by both fishermen and anatomists, was that you
could not really tell male from female, nor, indeed, ever find an eel
(that is, a common eel, as distinguished from the much larger and
well-known conger eel) which was ripe, or, indeed, showed any signs of
having either roe or milt within it. A popular legend exists that eels
are produced by the “vivification” of horse-hair. Occasionally in summer
a long, black, and very thin threadworm (called _Gordius_ by
naturalists) suddenly appears in great numbers in rivers, and these are
declared by the country-folk to be horse-hairs on their way to become
eels! I remember a sudden swarm of them one summer in the upper river at
Oxford. Really, they are parasitic worms which live inside insects for a
part of their lives, and leave them in summer, passing into the water.
Fanciful beliefs about aquatic creatures are common, because it is not
very easy to get at the truth when it is not merely at the bottom of a
well but at the bottom of a river or of the deep sea! The fishermen of
the east coast of Scotland, who think very highly of their own knowledge
and intelligence, believe that the little white sea-acorns or
rock-barnacles are the young of the limpets which live side by side with
them, and are scornful of those who deny the correctness of what they
consider an obvious conclusion!
A few years ago the Scandinavian naturalist, Petersen, showed that the
“silver” eels are a later stage of growth of the “yellow” eels; that
they acquire a silvery coat, and that the eye increases in size—as a
sort of “wedding dress,” just before they go down to the sea to breed. I
owe to Petersen’s kindness the coloured drawings of the heads of the
yellow and the silver eel reproduced in Plate I. These silver eels are
caught in some numbers about the Danish coast and river mouths, moving
downwards; and Petersen has been able to distinguish the males from
the females by finding the still incompletely formed milt and roe within
the silver eels. Not only that, but one of Petersen’s assistants at the
Danish Biological Station has found that you can tell the age of an eel
by the zones or rings shown by its scales, when examined with a
microscope, just as the age of trees can be told by the annual rings of
growth in the wood. Most people, even if familiar with eels, even cooks
who have skinned an eel, do not know that they have scales; but they
have,—very small ones. The age of other fishes has been similarly
ascertained by annual zones of growth marked on the scales; and lately
the age of plaice has been found to be conveniently given by zones of
growth formed annually on the little ear-stones which we find in the
liquid-holding sac of the internal ear. I am afraid many of my readers
will be surprised to learn that fishes have an internal hearing
apparatus similar to our own, also that they have olfactory organs, and,
in some cases, a well-grown tongue!
The power thus obtained of telling the age of an eel has led to the
following knowledge about them, namely, that female eels do not become
“silver” eels and “run down” before they are seven years old, and often
not till eight and a half years of age, or even sometimes eleven or
twelve years, when they are nearly 3 feet long. The male eel becomes
“silver” (instead of “yellow”) at an earlier age—four and a half
years,—and rarely defers his nuptial outburst until he is seven or
eight years old. The females of the same age are larger than the males;
a usual size for silver females of seven years old is a little over 2
feet, and of a silver male of the same age 20 inches.
The further facts which I am about to relate as to the migration and
reproduction of the common eel are of great interest. The common
“yellow” eels of our ponds and rivers, as we have seen, when they are
from five to seven years old and over, put on, as it were, a wedding
dress. They become “silver” eels, and descend the rivers to the sea.
There they produce their spawn. The young eels thus produced, when only
2 inches long, leave the sea. Every year they ascend the estuaries and
rivers of Europe as “elvers” in enormous numbers, their procession up
the rivers being known as “the eel-fare.”
Some eels, shut up in moats and ponds, never escape—they become more or
less “silver” and restless, but fail to get away. Others crawl up the
banks in wet, warm weather, when the ponds are full to the brim, and
over the meadows. They are found sometimes on their journey when they
“... have to pass
Through the dewy grass,”
and so to the river, and on to the marriage feast in the deep sea. The
fact is, that usually eels inhabit in large numbers the rivers and
streams, and have no difficulty in getting down to the sea when they are
adult. Those who, as young elvers, have wandered far off into sunken
ponds and reservoirs, are eccentric spirits who have lost the normal way
of life; like fellows of colleges in the old days, they have cut
themselves off from the matrimonial “running down,” but they have
compensations in quietude, abundant food, and a long life.
We now know where the silver eels go when they run down the rivers. They
go into the sea, of course; but we know more than that. It has now been
discovered that they make their way for many miles along the
sea-bottom—in some cases hundreds of miles—to no less a depth than 500
fathoms. In the Mediterranean they don’t have very far to go, for there
is very deep water near the land, and Professor Grassi found evidence of
their presence in the depths of the Straits of Messina. But the eels of
the rivers which empty into the North Sea and English Channel have much
farther to go; they have to go right out to the deep water of the
Atlantic, off the west coast of Ireland. That is the nearest point where
500 fathoms can be touched; there is no such depth in the North Sea nor
in the Channel. They never come back, and no one has ever yet tracked
them on their journey to the deep water. Yet we know that they go there,
and lay their eggs there, and that from these remote fastnesses a new
generation of eels, born in “the dark unfathomed depths of ocean,”
return every year in their millions as little “elvers” to the rivers
from which their parents swam forth in silver wedding dress. Soon, we
have reason to hope, by the use of suitable deep-sinking nets, we shall
intercept, in the English Channel, some of the silver eels on their way
to the Atlantic deeps. They must go in vast numbers, and yet no one has
yet come across them. How, then, do we know that the silver eels ever go
to this 500-fathom abysm?
[Illustration: FIG. 6.—Young stages of the common eel, drawn of the
natural size by Professor Grassi. A, The _Leptocephalus_, transparent
stage. D, the elver, or young eel, which is coloured, and of much
smaller size than the transparent, colourless creature by the change of
which it is produced. It is the elver which swims in millions up our
rivers. B and C are intermediate stages, showing the gradual change of A
into D.]
The answer is as follows: A very curious, colourless, transparent,
absolutely glass-like, little fish, 2½ inches long, oblong and
leaf-like in shape, has been known for many years as a rarity, to be
caught now and then, one at a time, floating near the top in summer seas
(Fig. 6). I used to get it at Naples occasionally many years ago, and it
has sometimes been taken in the English Channel. It is known by the name
“Leptocephalus.” Placed in a glass jar full of sea-water it is nearly
invisible on account of its transparency and freedom from colour. Even
its blood is colourless. The eyes alone are coloured, and one sees these
as two isolated black globes moving mysteriously to the right and the
left as the invisible ghostly fish swims around. Twenty years ago one of
these kept in an aquarium at Roscoff, in Brittany, gradually shrunk in
breadth, became cylindrical, coloured and opaque, and assumed the
complete characters of a young eel! To cut a long story short, these
Leptocephali were found twelve years ago in large numbers in the deep
water (400 fathoms) of the Straits of Messina by the Italian naturalists
Grassi and Calandruccio, and they conclusively showed that they were the
young phase—the tadpole, as it were—of eels. They showed that
different kinds of eels—conger eels, the Muræna, and the common
eel—have each their own kind of transparent “Leptocephalus-young-phase,”
living in but also above the very deep water, in which they are hatched
from the eggs of the parent eels. The Leptocephalus-young when hatched,
grow rapidly, and ascend to near the surface immediately above the deep
water, and are caught at depths of ten to a hundred fathoms. To become
“elvers,” or young eels, they have to undergo great change of shape and
colour, and actually shrink in bulk—a process which has now been
completely observed and described. It is not surprising that their true
nature was not at first recognised. The proof that the silver eels of
North and West Europe go down to the 500-fathom line off the Irish
coast, in order to lay their eggs, is that the Danish naturalist Schmidt
and his companions discovered there two years ago, above these great
depths (and nowhere else), by employing a special kind of fine-meshed
trawling net, many thousands of the flat, glass-like
“Leptocephalus-young-stage,” or tadpole of the common eel, and traced
them from there to their entrance into the various rivers. They showed
that the Leptocephali gradually change on the way landward into eel-like
“elvers.”
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.
X
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.
A very interesting fact, which goes a long way to establish the view
that the European domesticated horse is derived from the Mongolian wild
horse, comes to us in a most striking way from some of the most ancient
records of the human race. In the South of France the contents of caves
formerly inhabited by men have been dug out and examined with increasing
care and accuracy of late years, though first investigated fifty years
ago. Similar caves, though not so prolific of evidences of human
occupation, have been explored in England (Kent’s Cavern at Torquay, and
others). The astounding fact has now become quite clear that these caves
were inhabited by men of no mean capacity from 50,000 to 250,000 years
ago, when bone harpoons, flint knives, flint scrapers, and bone
javelin-throwers were the chief weapons in use, when these islands were
solidly joined to the European continent, when a sheet of glacial ice,
alternately retreating and extending, covered the whole of Northern
Europe, and when the mammoth, rhinoceros, hyena, lion, bear, bison,
great ox, horse, and later the reindeer, inhabited the land and were
hunted, eaten, and utilised for their bone, tusks, and skin by these
ancient men. I revert to this subject in a later article (page 371), but
would merely say now that it is all as certain and well-established a
chapter in man’s history as that of the ancient Egyptians, who are
really quite modern (dating from 8000 years at most) as compared with
these cave-men of 50,000 years ago, and the even earlier races which
preceded them in Europe.
The bones of the animals killed and eaten by the cave-men are found in
some cases in enormous quantities. In one locality in France the bones
of as many as 80,000 horses (which had been cooked and eaten) have been
dug up and counted! The most wonderful and extraordinary thing about
these cave-men is that they carved complete rounded sculptures, high
reliefs, low reliefs, and line-engravings on mammoth’s ivory, on
reindeer horn, on bones, and on stones—the line-engravings being the
latest in date, as shown by their position in the deposits on the floor
of the caves, which are often as much as twenty feet or thirty feet in
thickness! Not only that, but these carvings are often real works of
art, extremely well drawn, and showing not mere childish effort but work
which was done with the intention and control of an artist’s mind.
An immense number of these carvings are now known. I have before me one
of the most recent publications on the subject—a series of plates
showing the carvings collected from caves in the Pyrenees, the Dordogne,
and the Landes by M. Piette, who recently died. I have examined his
collection and others of the same kind in the great Museum of St.
Germain, near Paris. We have in London some of the earlier collections,
and especially that of the Vicomte de Lastic, to purchase which my old
friend Sir Richard Owen journeyed to the Dordogne in the winter of 1864.
Many animals, as well as some human beings (Fig. 7), are represented in
these carvings—the mammoth itself, carved on a piece of its own ivory,
is among them, and a good many represent the horse (Fig. 8). Now it is a
fact that the carvings of the horses of that period undoubtedly
represent a horse which is identical in proportions, shape of head,
mane, and tail, with the wild Mongolian horse, and is unlike in those
points to modern European horses, or to the Arabian horse.
[Illustration: FIG. 7.—Drawing (of the actual size of the original) of
an ivory carving (fully rounded) of a female head. The specimen was
found in the cavern of Brassempouy, in the Landes. It is of the earliest
reindeer period, and the arrangement of the hair or cap is remarkable.]
[Illustration: FIG. 8.—Drawing (of the actual size of the original) of
a fully rounded carving in reindeer’s antler of the head of a neighing
horse. The head resembles that of the Mongolian horse. This is one of
the most artistic of the cave-men’s carvings yet discovered. It is of
the Palæolithic age (early reindeer period), probably not less than
fifty thousand years old. It was found in the cavern of Mas d’Azil,
Ariège, France, and is now in the museum of St. Germain.]
It was, until the discoveries of M. Piette, held that though the
cave-men killed, ate, and made pictures of the horse of those remote
days, yet that they did not tame it, put a halter or a bridle on it, and
make use of it. Some of the carvings figured by M. Piette leave,
however, no room for doubt that the cave-men fitted a bridle to the head
and muzzle of the horse. These carvings (Fig. 9) show a twisted thong
placed round the nose and passing near the angle of the mouth where it
is possible, though not certain, that a “bit” was inserted. Connected
to this main encircling thong are four twisted cords (on each side of
the head), which run horizontally backwards, and the two lower of these
are joined by a flat, plate-like piece, which is ornamented. The whole
apparatus is further connected to a twisted cord on each side, which
runs towards the back of the head, but it is not shown in the carving
what becomes of it. Thus it seems clear not only that the cave-men of
these remote ages were wonderful artists, but that they mastered and
muzzled the horse.
[Illustration: FIG. 9.—Drawing (of the actual size of the original) of
a flat carving in shoulder-bone, of a horse’s head, showing twisted
rope-bridle and trappings. _a_ appears to represent a flat ornamented
band of wood or skin connecting the muzzling rope _b_ with other pieces
_c_ and _d_. This specimen is from the cave of St. Michel d’Arudy, and
is of the reindeer period. This, and others like it, are in the museum
of St. Germain.]
Some of the engravings of horses’ heads seem to indicate the existence
of a horse alongside the commoner form with a narrower, more tapering
face, and may possibly be due to the introduction, even at that remote
period, of another race distinct from the Northern or Mongolian wild
horse. That this admixture of a distinct and more slender horse with the
Northern horse has taken place over and over again in historical times
is a matter of knowledge. The question is, when did it first take place,
and where did the more slender horse come from? In later days we know
this more shapely breed as the Arab and the Barb, and the introduction
of its blood at various times into the more Northern stock is well
ascertained. The latest great historical case of such admixture is the
production of the English thoroughbred in the eighteenth century by
such sires as the Darley Arabian, the Godolphin Barb, and the Brierley
Turk, whose blood is transmitted to modern racehorses through the great
historic sires, Herod, Matchem, and Eclipse, the ancestors of
practically all modern racehorses.