my own experience I should suppose, that in all the habitable parts of
the globe certain water-flies exist wherever there is running water.
Even in the most ardent temperature, gnats and musquitoes are found,
which lay their congeries of eggs on the water, which, when hatched,
become first worms, afterwards small shrimp-like aurelia, and lastly
flies. There are a great number of the largest species of these flies on
stagnant waters and lakes, which form a part of the food of various
fishes, principally of the carp kind: but the true fisherman’s
flies,—those which are imitated in our art, principally belong to the
northern, or at least temperate part of Europe, and I believe are
nowhere more abundant than in England. It appears to me, that since I
have been a fisherman, which is now the best part of half a century, I
have observed in some rivers where I have been accustomed to fish
habitually, a diminution of the numbers of flies. There were always some
seasons in which the temperature was favourable to a quantity of fly;
for instance, fine warm days in spring for the grannam, or brown fly;
and like days in May and June for the alder-fly, May-fly, and stone-fly;
but I should say that within these last twenty years I have observed a
general diminution of the spring and autumnal flies, except in those
rivers which are fed from sources that run from chalk, and which are
perennial—such as the Wandle, and the Hampshire and Buckinghamshire
rivers; in these streams the temperature is more uniform, and the
quantity of water does not vary much. I attribute the change of the
quantity of flies in the rivers to the cultivation of the country. Most
of the bogs or marshes which fed many considerable streams are drained;
and the consequence is, that they are more likely to be affected by
severe droughts and great floods—the first killing, and the second
washing away the larvæ and aurelias. May-flies thirty years ago were
abundant in the upper part of the Teme river in Herefordshire, where it
receives the Clun: they are now rarely seen. Most of the rivers of that
part of England, as well as of the west, with the exception of those
that rise in the still uncultivated parts of Dartmoor and Exmoor, are
rapid and unfordable torrents after rain, and in dry summers little more
than scanty rills; and Exmoor and Dartmoor, almost the only considerable
remains of those moist, spongy, or peaty soils, which once covered the
greatest part of the high lands of England, are becoming cultivated, and
their sources will gradually gain the same character as those of our
midland and highly-improved counties. I cannot give you an idea of the
effects of peat mosses and grassy marshes on the water thrown down from
the atmosphere, better, than by comparing their effects to those of
roofs of houses of thatched straw, as contrasted with roofs of slate, on
a shower of rain. The slate begins to drop immediately, and sends down
what it receives in a rapid torrent, and is dry soon after the shower is
over. From the sponge-like roof of thatch, on the contrary, it is long
before the water drops; but it continues dropping and wet for hours
after the shower is over and the slate dry.
POIET.—You spoke just now of the gillaroo trout, as belonging only to
Ireland. I can, however, hardly bring myself to believe, that such a
fish is not to be found elsewhere. For lakes with shell-fish and char
are common in various parts of Europe, and as the gillaroo trout is
congenerous, it ought to exist both in Scotland and the Alpine
countries.
HAL.—It is not possible from analogies of this kind to draw certain
inferences. Subterraneous cavities and subterranean waters are common in
various countries, yet the Proteus Anguinus is only found in two places
in Carniola—at Adelsburg and Sittich. As I mentioned before, I have
never yet met with a gillaroo trout except in Ireland. It is true, it is
only lately that I have had my attention directed to this subject, and
other fishermen or naturalists may be more fortunate.
POIET.—Have you ever observed any other varieties of the trout kind,
which may be considered as, like the gillaroo, forming a distinct
species?
HAL.—I think the par, samlet, or brandling, common to most of our
rivers, which communicate with the sea, has a claim to be considered a
distinct species; yet the history of this fish is so obscure, and so
little understood, that, perhaps, I ought not to venture to give an
account of it. But in doing so, you will consider me as rather asking
for new information, than as attempting a satisfactory view of this
little animal.
ORN.—I have seen this fish in the rivers of Wales and Herefordshire, and
have heard it asserted, on what appeared to me good authority, that it
was a mule,—the offspring of a trout and a salmon.
HAL.—This opinion, I know, has been supported by the fact, that it is
found only in streams, which are occasionally visited by salmon; yet I
know no direct evidence in favour of the opinion, and I should think it
much more probable, if it be a mixed race, that it is produced by the
sea trout and common trout. In a small river, which runs into the Moy,
near Ballina in Ireland, I once caught in October a great number of
small sea trout, which were generally about half-a-pound in weight, and
were all _males_; and unless it be supposed, that the females were in
the river likewise, and would not take the fly, these fish, in which the
spermatic system was fully developed, could only have impregnated the
ova of the common river trout. The sea trout and river trout are,
indeed, so like each other in character, that such a mixture seems
exceedingly probable; but I know no reason why such mules should always
continue small, except that it may be a mark of imperfection. The only
difference between the par and common small trout is in the colours, and
its possessing one or two spines more in the pectoral fin. The par has
large blue or olive bluish marks on the sides, as if they had been made
by the impression of the fingers of a hand; and hence the fish is called
in some places _fingerling_. The river and sea trout seem capable of
changing permanently their places of residence; and sea trout appear
often to become river trout. In this case they lose their silvery
colour, and gain more spots; and in their offspring these changes are
more distinct. Fish, likewise, which are ill-fed remain small; and pars
are exceedingly numerous in those rivers where they are found, which are
never separated from the sea by impassable falls; from which I think it
possible that they are produced by a cross between sea and river trout.
The varieties of the common trout are almost infinite; from the great
lake trout, which weighs above 60 or 70lbs., to the trouts of the little
mountain brook or small mountain lake, or tarn, which is scarcely larger
than the finger. The smallest trout spawn nearly at the same time with
the larger ones, and their ova are of the same size; but in the large
trout there are tens of thousands, and in the small one rarely as many
as forty,—often from ten to forty. So that in the physical constitution
of these animals, their production is diminished as their food is small
in quantity; and it is remarkable, that the ova of the large and
beautiful species which exist in certain lakes, and which seem always to
associate together, appear to produce offspring, which, in colour, form,
and power of growth and reproduction, resemble the parent fishes; and
they generally choose the same river for their spawning. Thus, in the
lake of Guarda, the Benacus of the ancients, the magnificent trout, or
_Salmo fario_, which in colour and appearance is like a fresh run
salmon, spawns in the river at Riva, beginning to run up for that
purpose in June, and continuing to do so all the summer; and this river
is fed by streams from snow and glaciers in the Tyrol, and is generally
foul: whilst the small spotted common trouts, which are likewise found
in this lake, go into the small brooks, which have their sources not far
off, and in which, it is probable, they were originally bred. I have
seen taken in the same net small fish of both these varieties which were
as marked as possible in their characters:—one silvery, like a young
salmon, blue on the back, and with small black spots only; the other,
with yellow belly and red spots, and an olive-coloured back. I have made
similar observations in other lakes, particularly in that of the Tarun
near Gmunden, and likewise at Loch Neah in Ireland. Indeed, considering
the sea trout as the type of the species _trout_, I think all the other
true trouts may not improperly be considered as varieties, where the
differences of food and of habits have occasioned, in a long course of
ages, differences of shape and colours, transmitted to offspring in the
same manner as in the variety of dogs, which may all be referred to one
primitive type.[4]
PHYS.—I am somewhat amused at your idea of the change produced in the
species of trout by the formation of particular characters by particular
accidents, and their hereditary transmission. It reminds me of the
ingenious but somewhat unsound views of Darwin on the same subject.
HAL.—I will not allow you to assimilate my views to those of an author,
who, however ingenious, is far too speculative; whose poetry has always
appeared to me weak philosophy, and his philosophy indifferent poetry:
and to whom I have been often accustomed to apply Blumenbach’s saying,
that there were many things new and many things true in his doctrines;
but that what was new was not true, and what was true was not new.
POIET.—I think Halieus is quite in the right to be a little angry at
your observation, Physicus, in making him a disciple of a writer, who,
as well as I can recollect, has deduced the _genesis_ of the human
being, by a succession of changes dependant upon irritabilities,
sensibilities, and appetencies, from the _fish_; blending the wild
fancies of Buffon with the profound ideas of Hartly, and thus
endeavouring to give currency to an absurd romance, by mixing with it
some philosophical truths. I hope your parallel will induce him to do us
the favour to state his own notions more at large.
HAL.—Physicus has mistaken me; and I will explain. What I mentioned of
the varieties of dogs as sprung from one type, he will, I am sure, allow
me to apply, with some modifications, to all our cultivated breeds of
animals, whether horses, oxen, sheep, hogs, geese, ducks, turkies, or
pigeons; and he will allow, that certain characters gained by accidents,
either from peculiar food, air, water, or domestic treatment, are
transmitted to, and often strengthened in the next generation; the
qualities being, as it were, doubled when belonging to both parents, and
retained in spite of counteracting causes. It will be sufficient for me
to mention only a few cases. The blood-horse of Arabia, is become the
favourite of the north of Europe, and the colts possess all the superior
qualities of their parents, even in the polar circle. The offspring of
the Merino sheep retain the fineness of their wool in England and
Saxony. Poultry, bantams, tumbling and carrier pigeons, geese, ducks,
turkies, &c., all afford instances of the same kind; and in the goose
and duck, not only is the colour of the feathers changed, but the form
of the muscles of the legs and wings; those of the wings, being little
employed, become weak and slender; those of the legs, on the contrary,
being much used, are strong and fleshy; and it is well to know this, as,
in the young birds, the muscles of the legs and thighs are the best
parts for the epicure, a large quantity of flesh being developed there,
but not yet hardened or rendered tough by exercise. These facts are of
the same kind and depend on the same principles, as the peculiarity of
the breeds or races in trouts. Fish in a clear cool river, that feed
much on larvæ, and that swallow their hard cases, become yellower, and
the red spots increase so as to outnumber the black ones; and these
qualities become fixed in the young fishes, and establish a particular
variety. If trout from a lake, or another river of a different variety,
were introduced into this river, they would not at once change their
characters; but the change would take place gradually. Thus I have known
trout from a lake in Scotland, remarkable for their deep red flesh,
introduced into another lake, where the trout had only white flesh, and
they retained the peculiar redness of their flesh for many years. At
first they all associated together in spawning in the brook which fed
the lake, but those newly introduced were easily known from their darker
backs and brighter sides. By degrees, however, from the influence of
food and other causes, they became changed; the young trout of the
introduced variety had flesh less red than their parents; and in about
twenty years the variety was entirely lost, and all the fish were in
their original white state. A very speculative reasoner might certainly
defend the hypothesis, of the change of _species_ in a long course of
ages, from the establishment of particular characters as hereditary. It
might be said, that trout, after having thickened their stomachs by
feeding on larvæ with hard cases, gained the power of eating shell-fish,
and were gradually changed to gillaroos and to char; their red spots and
the yellow colour of their belly and fins increasing. In the same manner
it might be said, that the large trout which feed almost entirely on
small fishes, gained more spines in the pectoral fins, and became a new
species; but _I_ shall not go so far, and I know no facts of this kind.
The gillaroo and the char appear always with the same characters: and I
have never seen any fish that seemed in a state of transition from a
trout to gillaroo or a char; which I think, must have been the case if
such changes took place. I hope, after this explanation, Physicus will
not find any analogy between my ideas and those of a school, to which I
am not ambitious of being thought to belong; and that he will allow my
views to be sound, or at least founded upon correct analogies.
POIET.—Do you know any facts of a similar kind in confirmation of your
idea that the par is a mule?
HAL.—I have heard of similar instances, but I cannot say I have myself
witnessed them. The common carp and the cruscian are said to produce a
mixed race, and likewise the rud and the roach; but I have never paid
much attention to varieties of the carp kind. A friend of mine informed
me, that in a branch of the Test, into which graylings had recently been
introduced, his fisherman caught a fish, which appeared to be from a
cross between the trout and grayling, having the high back fin of the
grayling, and the head and spots of the trout: this is the more
remarkable, if correct, as the grayling spawns in the late spring, and
the trout in the late autumn or winter: yet I _do_ recollect that I once
took a grayling in the end of November, in which the ova were so large,
as nearly to be ready for protrusion. The fisherman of the Gründtl See,
in Styria, informed me, that he had seen a fish which he believed to be
a mule between the trout and char, the fins of which resembled those of
a trout, though the body was in other respects like that of a char. The
seasons at which these two species spawn approach nearer to each other;
but the char spawns in still and the trout in running water. In general
the trout are mature before the char, yet I have seen in the
Leopoldstein See, in Styria, a female char, of which the eggs were
almost fully developed as early as June: the fisherman of the Gründtl
See said, that these peculiar fish were very rare, and that he caught
only one in about 500 char. It is not, I think, impossible, that it may
be an umbla, a fish that might be expected to be found in that deep,
cold, Alpine lake, a peculiar species and not a mixed variety. It is a
fertile and very curious subject for new experiments, that of crossing
the breeds of fishes, and offers a very interesting and untouched field
of investigation, which I hope will soon be taken up by some enlightened
country gentleman, who in this way might make not only curious but
useful discoveries.
POIET.—So much science would be required to make these experiments with
success, and there would be so many difficulties in the way of
preserving fishes at the time they are proper for reproduction, that I
fear very few country gentlemen would be capable of prosecuting the
inquiry.
HAL.—The science required for this object is easily attained, and the
difficulties are quite imaginary. The impregnation of the ova of fishes
is performed out of the body, and it is only necessary to pour the
seminal liquor from the melt upon the ova in water. Mr. Jacobi, a German
gentleman, who made many years ago experiments on the increase of trout
and salmon, informs us, that the ova and melt of mature fish, recently
dead, will produce living offspring. His plan of raising trout from the
egg was a very simple one. He had a box made with a small wire grating
at one end in the cover, for admitting water from a fresh source or
stream, and at the other end of the side of the box there were a number
of holes to permit the exit of the water: the bottom of the box was
filled with pebbles and gravel of different sizes, which were kept
covered with water that was always in motion. In November or the
beginning of December, when the trout were in full maturity for
spawning, and collected in the rivers for this purpose upon beds of
gravel, he caught males and females in a net, and by the pressure of his
hands, received the ova in a basin of water, and suffered the melt or
seminal fluid to pass into the basin; and after they had remained a few
minutes together, he introduced them upon the gravel in the box, which
was placed under a source of fresh, cool, and pure water. In a few weeks
the eggs burst, and the box was filled with an immense number of young
trout, which had a small bag attached to the lower part of their body
containing a part of the yolk of the egg, which was still their
nourishment. In this state they were easily carried from place to place
in confined portions of fresh water for some days, requiring apparently
no food; but, after about a week, the nourishment in their bag being
exhausted, they began to seek their food in the water, and rapidly
increased in size. As I have said before, Mr. Jacobi assures us, that
the experiment succeeded as well with mature fish, that had been killed
for the purpose of procuring the roe and melt, these having been mixed
together in cold water immediately after they were taken out of the
body. I have had this experiment tried twice, and with perfect success,
and it offers a very good mode of increasing to any extent the quantity
of trout in rivers or lakes, for the young ones are preserved from the
attacks of fishes, and other voracious animals or insects, at the time
when they are most easily destroyed, and perfectly helpless. The same
plan, I have no doubt, would answer equally well with grayling or other
varieties of the salmo genus. But in all experiments of this kind, the
great principle is, to have a constant current of fresh and aerated
water running over the eggs. The uniform supply of air to the fœtus in
the egg is essential for its life and growth, and such eggs as are not
supplied with water saturated with air are unproductive. The
experimenter must be guided exactly by the instinct of the parent
fishes, who take care to deposit the impregnated eggs, that are to
produce their offspring, only in sources continually abounding in fresh
and aerated water.
PHYS.—But as every species of fish has a particular and usually
different time for spawning, I do not see how it could be contrived to
cross their breeds, or how the ova of a trout, which spawns in December,
could be impregnated by the seminal fluid of the grayling, which spawns
in May; for I conclude it would be impossible to preserve the eggs of a
fish out of the body in a state in which they could retain or recover
their vitality.
HAL.—I believe I mentioned before, that I had found instances, in which
the ova of fish were developed at a different period from their natural
one; and I have no doubt, that a little inquiry respecting the habits of
fishes would enable us to acquire a knowledge of the circumstances,
which either hasten or retard their maturity. Plenty of food and a
genial season hasten the period of their reproduction, which is delayed
by want of proper nourishment, and by unfavourable weather. Males and
females likewise, confined from each other, have their generative powers
impeded; and trout, grayling, and salmon, will not deposit their ova
except in running water; so that by keeping them in tanks, the period of
their maturity might be considerably altered. I have seen char even,
which had been kept in confined water from September till July; and so
slow had been the progress of the ova, that they appeared to be about
this time fit for exclusion, though, in the natural course of things,
they would have been ripe in the end of October of the year before. By
attending to and controlling all these circumstances, I have no doubt
many interesting experiments might be made, as to the possibility of
modifying the varieties of the salmo, by impregnating the ova of one
species with the seminal fluid of another. With fishes of other genera
the task would be still more easy. Carp, perch, and pike, deposit their
ova in still water in spring and summer, when it is supplied with air by
the growth of vegetables: and it is to the leaves of plants, which
afford a continual supply of oxygen to the water, that the impregnated
eggs usually adhere; so that researches of this kind might be conducted
within doors in close vessels, filled with plants, exposed to the sun. I
have myself kept minnows and sticklebacks alive for many months in the
same confined quantity of water, containing a few confervæ; and their
ova and melt increased in the same manner, as if they had been in their
natural situation.
ORN.—I conclude from your statements, Halieus, that nothing more is
required for the production of fishes from impregnated eggs, than a
constant supply of water of a certain temperature furnished with air;
and of course the same principles will apply to fishes of the sea.
HAL.—There can be no doubt of it: and fishes in spawning time always
approach great shallows, or shores covered with weeds, that, in the
process of their growth, under the influence of the sunshine, constantly
supply pure air to the water in contact with them.
POIET.—In every thing belonging to the economy of nature, I find new
reasons for wondering at the designs of Providence,—at the infinite
intelligence by which so many complicated effects are produced by the
most simple causes. The precipitation of water from the atmosphere, its
rapid motion in rivers, and its falls in cataracts, not only preserve
this element pure, but give it its vitality, and render it subservient
even to the embryo life of the fish; and the storms which agitate the
ocean, and mingle it with the atmosphere, supply at once food to marine
plants, and afford a principle of life to the fishes which inhabit its
depths. So that the perturbation and motion of the winds and waves
possess a use, and ought to impress us with a beauty higher and more
delightful even than that of the peaceful and glorious calm.
THIRD DAY.
HALIEUS—POIETES—ORNITHER—PHYSICUS.
SCENE—DENHAM.
_Morning._
HAL.—YOU will soon take your leave, gentlemen, of this agreeable villa,
but we must catch at least two brace of trout, to carry with us to
London as a present for two worthy patrons of the angle. For though I
know our liberal host will have a basket of fish packed up for each of
our party, yet fish taken this morning will be imagined a more
acceptable present than those caught yesterday. The May-fly is already
upon the water, though not in great quantity, and it will consequently
be more easy to catch the fish, which I see are rising with great
activity. I advise you to go to the deep water below, where you will
find the largest fish, and I will soon follow you.
POIET.—I hope I shall catch a large fish,—a companion to that which
Ornither took yesterday with a natural fly.
[_Halieus leaves them fishing, and returns to the house; but soon comes
back and joins his companions, whom he finds fishing below in the
river._]
HAL.—Well, gentlemen, what sport?
POIET.—The fish are rising every where; but though we have been throwing
over them with all our skill for a quarter of an hour, yet not a single
one will take, and I am afraid we shall return to breakfast without our
prey.
HAL.—I will try; but I shall go to the other side, where I see a very
large fish rising. There!—I have him at the very first throw. Land this
fish, and put him into the well. Now I have another; and I have no doubt
I could take half a dozen in this very place, where you have been so
long fishing without success.
PHYS.—You must have a different fly; or have you some unguent or charm
to tempt the fish?
HAL.—No such thing. If any of you will give me your rod and fly, I will
answer for it, I shall have the same success. I take your rod,
Physicus.—And lo! I have a fish!
PHYS.—What can be the reason of this? It is perfectly inexplicable to
me. Yet Poietes seems to throw as light as you do, and as well as he did
yesterday.
HAL.—I am surprised, that you, who are a philosopher, cannot discover
the reason of this. Think a little.
ALL.—We cannot.
HAL.—As you are my scholars, I believe I must teach you. The sun is
bright, and you have been, naturally enough, fishing with your backs to
the sun, which, not being very high, has thrown the shadows of your rods
and yourselves upon the water, and you have alarmed the fish, whenever
you have thrown a fly. You see I have fished with my face towards the
sun, and though inconvenienced by the light, have given no alarm. Follow
my example, and you will soon have sport, as there is a breeze playing
on the water.
PHYS.—Your sagacity puts me in mind of an anecdote which I remember to
have heard respecting the late eloquent statesman, Charles James Fox;
who, walking up Bond-street from one of the club-houses with an
illustrious personage, laid him a wager, that he would see more cats
than the Prince in his walk, and that he might take which side of the
street he liked. When they got to the top, it was found, that Mr. Fox
had seen thirteen cats, and the Prince not one. The royal personage
asked for an explanation of this apparent miracle, and Mr. Fox said,
“Your Royal Highness took, of course, the shady side of the way, as most
agreeable; I knew that the sunny side would be left to me, and cats
always prefer the sunshine.”
HAL.—There! Poietes, by following my advice you have immediately hooked
a fish; and while you are catching a brace, I will tell you an anecdote,
which as much relates to fly-fishing as that of Physicus, and affords an
elucidation of a particular effect of light.