the flower is only a useful structure in
the air.
One of the most interesting examples of
these advanced plants which have returned
to the water is the water buttercup (Ranun-
culus aquatilis). Here we have a species
with showy flowers and very many of the
characteristics which are associated with
THE PAGEKttT OF NATURE
the typical land plant. In fact, now and is quite distinct. Here each leaf is little
again, when a small pond dries up in the more than a cluster of midribs and veins,
summer the water buttercup is able to per- giving a general appearance of so many green
sist, sending its roots deep into the mud hairs. These submerged leaves grow best
until such time as the pool fills again, in swiftly running water. In such positions
The two leaf-forms of the Water Buttercup ; the flat three-lobed
leaves on the flowering stem, which mostly float on the surface
of the water; and, quite distinct, the under-water foliage, in
which each leaf is little more than a cluster of midribs and
veins with a general appearance of so many green hairs.
Indeed, the plant is peculiarly fitted to make
the best of both worlds. The flowering
portion of the stem which rises above the
water bears flat three-lobed leaves which
mostly float on the surface of the water,
although, when growth is very vigorous,
they may stand up quite clear of the pool.
Beneath the water the character of the foliage
the plant becomes more definitely an aquatic
and the pretty white flowers are not nearly
so freely produced as when the buttercup
is growing in stagnant waters. The plant
on these occasions does not rely so much on
seed production for propagation, but chiefly
upon the broken stems which the stream
carries to fresh situations lower down.
254
WILD FLOWERS AND THEIR WAYS
In almost any long portion of the stem of
the water buttercup it is possible to see
each stage in the transition from the air
foliage to that which is submerged. Close
to the flower heads there are three or four
of the flat-lobed leaves ; just below the
water there will be organs which are partly
flat and partly hair-like. Then at last one
reaches the point where the entire foliage is
" filiform " or thread-like. Certainly the
water buttercup is one of the most in-
teresting plants, from the evolutionary
point of view, which occurs in the British
Islands.
The thread-like leaf is widely found among
water plants which belong to distinct
orders. This is because it is so well suited
to the part which it has to play. Water
does not contain so much carbonic acid as
the atmosphere, and this fact has led to the
development of the filiform leaf. In the
air above, where there is no shortage of
carbonic acid gas, the leaves can expand
to their fullest extent, but atmospheric food
supplies are short in the water, hence the
totally submerged foliage is reduced to a
cluster of midribs and veins.
The water buttercup is a variable plant
in the general manner of its growth. In a
river the stems may be several feet in length,
whilst in a shallow pond they are perhaps
no more than a few inches. Several
varieties have been regarded as definite
species by botanists, although any one plant
may evidence such a diversity in leaf forma-
tion that classification is difficult. The ivy-
leaved crowfoot (Ranunculus hederaceus) is,
however, easily recognized owing to the fact
that it is always much smaller than the
common species.
The pretty white flowers of the Water Buttercup are more freely produced when the
plant is growing in stagnant waters.
255
Strange Facts of Fish Life
2.-THE LIFE-STORY OF THE EEL
By F. MARTIN DUNCAN, F.R.M.S., F.R.P.S., F.Z.S.
"With photographs by the Author
The larva, or
FROM the days of Aristotle down to
the present century the birth and
early life-history of our common eel
(Anguilla vulgaris) remained an unsolved
mystery. Many and varied have been the
theories pro-
pounded by
philosophers and
laymen through
the passing
centuries as to the
breeding of the eel;
from the theory
of a spontaneous
generation, the
outcome of putre-
faction, to the pro-
duction of eels by
steeping horsehair,
preferably from
the body of a
stallion, in a
shallow pool !
Even the identity
of the sexes was not established until the
latter half of the nineteenth century. A
hundred years elapsed between the dis-
covery of the female and the male eel, the
former being first described by Mondini
in 1777, and the latter by Syriski in 1874.
Another twenty years elapsed before the
Italian zoologists, Grassi and Calandruccio,
published in 1896 their epoch-making dis-
covery of the young or larval eel ; hut
still the earliest stages, the period of time
covered by the childhood of the eel and
the actual breeding grounds, remained un-
known. Now, however, after some six-
teen or seventeen years of patient and
untiring investigation, the great marine
biologist, Dr. Johs. Schmidt, of Copenhagen,
has at last solved the mystery and completed
young
literally "s^rall head '), of the common eel of
British ponds and rivers. At one time varia-
tions in shape, size, and structure, among the
specimens, led to their being described as
the eel, a life-history that must for ever rank
as one of the most intensely interesting and
extraordinary in the whole realm of Nature.
The long period which elapsed between
the actual discovery and demonstration of
the sexes may be
traced to three
causes. Firstly
because the male
eel always remains
nearer the sea,
living chiefly in the
brackish waters of
the mouths and
estuaries of rivers,
rarely ascending
far above the reach
of tides. Secondly,
b ecause he is
smaller than the
female, seldom
exceeding
(Lfptot ephalus brevirosiris ,
different species. Photographed at the length
of 2 centimetres.
inches in length,
and, possessing a
broad head and snout, was therefore looked
upon as a variety, if not a distinct species,
known as the rig or broad-nosed eel. While
thirdly, and this applies equally to both
sexes, the sexual organs do not begin to
mature or attain an easily recognized size
until the eels have passed out to sea and are
well on their way to their breeding grounds.
The female eel attains much greater
size than the male ; specimens well over
three feet in length are occasionally captured.
Because of her more pointed snout and
narrower head the female is popularly known
as a " sharp-nosed eel." The females are
to be found in all rivers, and also in dykes,
ponds and lakes far inland ; they reach
these isolated waters by travelling overland
generally at night, when the herbage of the
our knowledge of the entire life-history of fields and meadows are damp with rain and
256
STRANGE FACTS OF FISH LIFE
dew. The eels are able to accomplish such
journeys by reason of the profuse slime
secreted by the skin, and also by the beauti-
ful mechanism of their gills, which enables
them to retain in the gill-cavity sufficient
water to keep the delicate folds or branchial
laminae afloat. In a live eel these gill-cavities
appear as a conspicuous swelling on each side
of the throat, and so long as they are rilled
with water the eel can remain on land
without fear of suffocation.
As eels of all sizes are to be found at all
seasons of the year in rivers, ponds and lakes,
often far from the sea, it is not very surprising
that the possibility of their real breeding
ground being far out in the depths of the
ocean remained long unsuspected, or that
until comparativelyrecent times
a vague but very general idea
existed that a certain propor-
tion bred in some mysterious
way in the inland waters, and
others in the sea.
Every autumn considerable
numbers of eels begin to pass
down the rivers towards the
open sea, and there is a regular
fishery carried on for these
migrants. They are caught in
wicker basket traps called " eel-
bucks " ; while farther north,
in Denmark and Sweden, they
are taken not only as they pass
down the rivers, but even as they journey
along the coasts, the traps being set from the
margin of the shore outwards in shallow
water down to a depth of about six fathoms.
This annual autumn migration, however, is
not composed of the whole eel population of
the ponds, lakes and rivers, but is confined
entirely to those individuals which have
begun to feel the sexual impulse. Eels
may remain in one district for many years ;
the period varies greatly according to sex,
climate, and food supply, so that it may range
from five to twenty years or longer before the
sexual instinct calls them back to the sea.
These years spent in the rivers and lakes are
devoted to feeding and growth. During
the whole of this time the eels are of a
greenish or yellowish colour, and are known
to fishermen as " yellow eels." Once the
migratory instinct begins to assert itself, the
eels cease to feed so voraciously, and their
bodies take on a metallic sheen, while their
pectoral fins become pointed and black in
colour. In this, their migratory dress, they
are known as " silver eels," their flesh is
firm and rich in fat, and they are eagerly
caught for the market. They have reached
the zenith of their size and strength, and are
in perfect condition to undertake the second
great journey of their lives, back to their
natural and only breeding grounds, far across
the ocean, whence they will never return.
Just as every autumn this great migra-
tion of adult eels takes place seawards, so
every spring sees the arrival of vast hosts of
tiny eels or " elvers," which ascend the rivers
from the sea all round our coasts. These
elvers, or " eel-fare," as they are called in
some counties, are slender, semi-trans-
Leptocephalus larva of the common eel, photographed at
the length of 4| centimetres. These larvae are transparent,
measure some 4| inches to 5 inches in length, and
resemble in shape a willow or eucalyptus leaf.
parent little creatures, measuring two or three
inches in length. The elvers are greedily
devoured by birds and fishes as they ascend
the rivers in dense masses, and are also
caught in hand nets, salted, and fried, to be
sold as " elver cakes " ; heavy toll, indeed,
is taken of the multitudes which annually
come up the rivers from the sea.
Although so small and transparent, the
elvers are otherwise fully developed, and
have the same shaped body, head, and fins,
and other characteristics of the adult eel.
Because no one had ever seen an elver that
was not a perfect eel in miniature, it was
at one time thought that the young must
hatch out from the egg more or less closely
resembling the adult in appearance. But
as the more accurate study of fishes began
to reveal the fact that the majority undergo
considerable changes in shape before taking
on the characteristic form of the adult,
grave doubts arose as to the probability of
19
257
THE PAGEANT OF NATURE
the early life-history of the eel being quite
so simple.
For the beginning of the story of our
knowledge of the life-history of the eel, we
must go back to the early 'fifties of the last
century, when certain small, leaf-like, trans-
parent fishes called Leptocephali (literally
" small heads "), chiefly obtained from the
Straits of Messina, began to attract con-
siderable attention. One of the earliest
accounts of these curious little fish,
written by Kaup, appears in a British
Museum catalogue published in 1856, in
Every spring vast numbers of elvers, or young eels, ascend the British
rivers from the sea. During the third autumn and winter of their
lives they undergo the remarkable change which gives them their
shape as elvers.
which twenty-two supposed species are
described, and amongst them one called the
Leptocephalus brevirostris was for the first
time figured. These little fish present
a very striking appearance, for they are
transparent, have very small heads, meas-
ure some 4J to 5 inches in length, and
resemble in shape a willow or euca-
lyptus leaf. Differences in shape, size, and
structure among the specimens led to their
being described as different species, and
various theories were propounded concern-
ing their nature, one being that they were
the larval stage of certain fishes related to
the red band fish. An American naturalist,
Theodore Gill, appears to have been the
first rightly to suspect that they were really
early larval forms of various species of eels,
for in 1864 he expressed the following
opinion on the subject : " I am almost cer-
tain that the typical Leptocephali are at least
the young of congers, and that Leptocephalus
morrisii is the young of the common conger
eel (Conger vulgaris)" Gill's surmise was
destined to be proved correct, and his
opinion was upheld by Dr. Giinther, of
the British Museum, who, however, pro-
pounded the extraordinary theory that these
little fishes were monstrosities, youngsters
who, having by some unknown means got
into unnatural conditions or unsuitable
environment, had
become Peter Pans
of the fish world,
and consequently
could not grow up
or pass through
their proper trans-
formations to the
adult form !
Finally, however,
Professors Grassi
and Calandruccio
conclusively
demonstrated that
the little fish
known to science
for so many years
as the Leptoce-
phalus brevirostris
was the true larva,
or young, of the
common eel. The
investigations o f
these Italian
naturalists were carried out in the Mediter-
ranean, for they were able to obtain large
numbers of the little Leptocephali in the
Straits of Messina, where they are brought to
the surface by the action of powerful whirl-
pools, which at certain seasons of the year
there reveal various forms of marine creatures
peculiar to the great depths of the ocean.
The identity of this early stage in the life-
history of the eel having been established,
the actual breeding grounds and early
history still remained to be discovered.
Patiently, through long years of untiring
investigation, Dr.Johs. Schmidt has gathered
material which at last has enabled him to
discover and chart the actual spawning
ground of the eel, and to trace its complete
life-history
STRANGE FACTS OF FISH LIFE
During the autumn and winter months
the eels, clad in their silvery dress, migrate
from the lakes and rivers of Great Britain,
of north and west Europe, from the Baltic
and the North Sea, and move out into the
Atlantic. There they shape their course
south-west through the ocean, with the
same unerring instinct as migrating birds,
following the same course as their ancestors
have done for countless generations. How
long that journey lasts is still uncertain, but
by marking numbers of these migrating eels
with small silver disks fastened to their
dorsal fins each
disk bearing a dis-
tinctive mark and
number it has
been possible to
obtain much in-
teresting informa-
tion concerning the
speed at which
they start upon
their long journey.
These marking ex-
periments were
carried out in
Sweden and Fin-
land, and the
marked eels re-
captured at places
lying nearer to the
open sea. In every
instance it was
shown that they
were heading for
the North Sea and
Atlantic Ocean.' These experiments proved
conclusively that considerable numbers of
the migrating eels were travelling at a
speed of at least 15 kilometres a day,
and had maintained this speed for seventeen
to thirty days before being recaptured. Once
these migrating eels reach the open North
Sea and Atlantic Ocean, however, they
disappear from our ken, for the trawl and
drifts nets of the fishing boats are unsuited
for their capture.
As it was found impossible to follow the
course of these adult migrating eels once
they had passed out into the Atlantic, it was
decided to attempt to trace the route by
which the little Leptocephali or larval eels
approach the coasts of north and west
Europe, and so, if possible, to track them
down to the unknown breeding ground.
The task was by no means an easy one.
Long cruises had to be made in ships more
or less properly equipped with special
apparatus for collecting these small fry,
which swim at varying depths, from 50 to
25 metres, and at times even at the surface
of the sea. Indeed, before sufficient data
could be collected, voyages of investigation
had been made ranging from America to
Egypt, and from Iceland to the Canary
Islands. But at long last the riddle was
solved, and the breeding ground of all
When they have donned their 1 migratory dress, eels are known as
" silver eels," and their flesh is firm and rich in fat. At this stage
they have reached the zenith of their size and strength.
European and British eels that is, the so-
called " common eel " (Anguilla vulgaris)
was discovered to be a certain area situated
in the western Atlantic, about 22 and 30
N. Lat., and about 48 and 65 W. Long.,
having its centre about equidistant from the
Leeward Islands of the West Indies and
Bermuda. There, spawning begins in early
spring and lasts well on into the summer,
and the tiny baby eels or Leptocephali, meas-
uring 7-15 mm. in length, are found swim-
ming at a depth of 200 to 300 metres from
the surface, where the sea water has a tem-
perature of about 20 C. The little creatures
grow rapidly during the early months oi
their lives, and in their first summer attain
an average length of 25 mm. They then
quit the great depths in which they were
259
THE PAGEANT OF NATURE
born and move up towards the surface
waters, large numbers being taken at 50
and 25 metres, and even close to the
surface.
Now, aided by the eastward movement of
the surface waters, these little larval eels
start upon their long journey across the
ocean towards the shores of Europe ; a
journey that will occupy the first three
years of their existence. During their first
summer they are in the western Atlantic,
west of 50 long. W. The second summer
Scales from body of an adult eel, greatly magnified,
showing seasonal growth.
finds them in the central Atlantic and grown
to 50-55 mm. in length. In the third
summer they arrive off the coastal banks of
Europe, and though still retaining their com-
pressed, leaf-shaped larval form, are full
grown and average about 75 mm. in length.
During this third autumn and winter pf
their lives they undergo the remarkable
change or retrograde metamorphosis, which
gives them their shape as tiny transparent
eels ; it is now that they move inshore
and make their way as " elvers," in count-
less numbers up the rivers and streams, and
find their way far inland into ditches, ponds
and lakes.
In working out this wonderful life-history,
Dr. Schmidt made another curious and in-
teresting discovery, namely, that the breed-
ing ground of the American eel (Anguilla
rostratd) is in close proximity to that of the
European. In fact, he discovered that there
are extensive areas where the larvae of the
two species are found living together in
considerable numbers. Yet, despite this
mingling in their early childhood, the two
species later separate and depart to their
respective continents ; no American eel has
ever reached the shores of Europe, and
no European eel has entered an American
river. The
natural factors
responsible for
this sorting out of
the two species
are full of in-
terest. The
breeding ground
of the American
eel has its centre
of production
somewhat farther
west and south
of that of the
European eel ;
while what we
may term the
early childhood
of the American
species that is,
the larval stages
spent near the
surface waters of
the ocean is
of much shorter
duration, only
occupying about one year, and conse-
quently too short a period of time in
which to make the long journey across
the ocean to the shores of Europe. There-
fore, these precocious American eels must
perforce seek a nearer landfall, and do indeed
make at once towards the shores of America
and the West Indies. The European eels,
on the other hand, taking nearly three times
as long over their larval stage development
have, with the help of the ocean currents and
their own active movements, travelled far
from the western part of the Atlantic, where
they were born, by the time they are ready
as tiny elvers to seek the coastal waters of
Europe and the British Isles, and to ascend
the rivers.
Note the bands
260
How the Reptiles Live
Photo: IV. y. Clarke.
The Smooth Snake, although said to be common in Dorset, Hampshire, Surrey
or Berks, is really rare. Its temper is uncertain; even when thought friendly and
tame, it will bite.
2.-HARMLESS SNAKES IN GREAT
BRITAIN
The Rare Smooth Snake and the Common Grass Snake
By P. CHALMERS MITCHELL, M.A., D.Sc., LL.D., F.R.S., C.B.E.
I WONDER why the smooth snake
(Coronella austriaca) bites. I have
never myself been able to find one in
Dorset, Hampshire, Surrey or Berks, the
few English counties in which it is said to
be common ; but I have often seen it in the
South of France or in the London Zoo, and
there is no doubt about its biting. It is
really rather a cross snake, always ready to
bite even when you think it has grown
friendly and tame. The ?dder when at-
tacked coils itself in a spring-like spiral
disk, the head raised in the middle, poised
and ready to strike. The smooth snake
noses you in a slow and almost friendly way,
but suddenly, without warning, chooses a
suitable place deliberately, say one of your
fingers, takes it into its mouth and almost
chews, holding on firmly, and gradually
pressing its teeth in. The bite has no venom
and is little more than a sharp pinch, hardly
ever drawing blood.
261
THE PAGEANT OF NATURE
Probably it is almost a mechanical habit inches to two feet, whilst the grass snake is
applied to man without any real intention often much longer. The shape is rather
of biting or hurting. The smooth snake similar, although the adder is stouter and
prefers lizards to any other food. It is more heavily built and has a broader head,
accustomed to glide among them, neither But the smooth snake has the curious habit
alarming them nor apparently paying any of swelling out the back of its mouth cavity,
attention to them, until suddenly it seizes giving its head something of the triangular
one of the active, wriggling little creatures, shape of that of an adder perhaps to be
holds on firmly to it until it can throw i.s connected with the power of a foreign rela-
coils over the struggling animal, slowly tive, Dasypeltis of tropical Africa, which is
smothering it, and not trying to swallow able to swallow a hen's egg several times
it until it is dead. It treats a mouse the thickness of its own head,
in the same way, a very different pro- Close inspection shows that the scales of
cedure from that of a poisonous snake, the smooth snake are smooth, without the
___ little keel which marks
those of the adder, and
that its pupil is round,
not a vertical slit as in
the adder ; but these
minute although im-
p o r t a n t differences
cannot be seen until
the snake has been
caught or killed.
There is an equal
difficulty about the
colouring. The adder
ought to be a brilliant,
almost black-and-
Photo: If. S. Ber ridge, F.Z.S.
The Smooth Snake is similar to the Adder in size and shape,
although the latter is stouter and has a broader head. Both
frequent the same kind of places dry and sunny spots and
avoid the damp and lush grass which Grass Snakes love.
white creature with a
clearly marked
diamond pattern along
the back. The smooth
snake ought to have
a silvery sheen, like
polished steel, with
A viper strikes almost instantaneously, little spots arranged in rows. Both are very
and then lets go, partly as if it feared that variable, and both are often so dimly coloured
the struggles of the dying animal might that the pattern cannot be made out at a
injure its delicate poison fangs, partly as if distance. Smooth snakes are generally
it knew that there was no need to take any dark greyish above with a red shade and red-
further trouble as the venom would speedily brown spots ; the under-surface is also dark
conquer the victim. Big constricting snakes, greyish with less red, and is often specked
like the boas and pythons, are also biters : with black and white.
they seize hold of their prey with their teeth, Smooth snakes, also like adders, are
and grip it until they can surround its body viviparous, bringing forth a family of from
with their coils.
six to ten, alive and wriggling, which have
It must be admitted, however, that there been hatched inside the body of the mother,