One day in November the postman brought Uncle George a small wooden box.
There were holes bored in the sides and top of it. The box, when opened,
seemed to be filled with damp moss; but when some of this moss was
removed there was found in the middle of the box a piece of folded
muslin.
[Illustration]
Hatching Bottle.
A. Supply pipe.
B. Exhaust pipe.
C. Trout Eggs.
Rearing Box.
C. Perforated zinc tray to fit box.
Uncle George laid the muslin on the table, and opened it out. It
contained a number of tiny pink balls, much smaller than peas.
“These are the trout eggs you promised to get for us, are they not?”
said Frank.
“They are,” said Uncle George, “and we must put them into running water
at once. I have a bottle here ready for them.”
Uncle George filled a wide-mouthed bottle with water from the tap and
placed the eggs in it. He then corked it with a cork in which he had
bored two holes.
Into each of the holes he had fitted a tube. One tube was long enough to
reach almost to the bottom of the bottle. The other was bent over the
outside of the bottle.
The straight tube was connected with the water tap by a piece of
indiarubber tubing. He then turned the tap on gently, so that the water
went in by the straight tube and came dripping out by the bent tube.
“Trout require a constant supply of fresh water,” he said. “Their eggs
are usually laid in shallow streams.
“Now, boys, I want you to watch these eggs and note down any changes you
see in them. You can remove the bottle from the tap at any time, but you
must not keep it more than fifteen minutes at a time, or your trout will
not hatch.”
At the end of a week the boys noticed two black dots and a coiled white
line in each egg.
In two weeks more some curious-looking creatures were seen wriggling
about among the eggs. As there were some empty egg-skins to be seen,
they guessed that these lively creatures must be young trout.
They were not a bit like fish. Each seemed to be made up of a long white
streak, which looked like the “backbone” of a fish, a big, clumsy yellow
bag with red veins running through it, and two large black spots that
looked like eyes.
In a few days all the eggs hatched out, and in place of the little pink
eggs there was a crowd of these wriggling creatures and a number of
empty egg-skins. The boys were puzzled, and Uncle George had to be
consulted.
[Illustration: Six Stages in Development of Trout.]
“I don’t think these were trout eggs,” said Frank. “The creatures that
came out of them are not a bit like fishes. They swim on their sides and
have a huge yellow bag attached to their bodies.”
“They _are_ young trout, I can assure you, Frank,” said his uncle
laughing. “If you remember, your tadpoles were not a bit like frogs when
they hatched out of the egg. These huge bags you talk of are called
‘yolks.’ Each trout when hatched is furnished with a huge yolk or food
supply.
“The tadpole, when hatched, has also got a yolk upon which he lives
without eating for four or five days. Our trout will require no food for
six weeks. During that time the yolk will become smaller and smaller,
and at last disappear entirely. While the yolk is shrinking, you will
notice that the creature gradually assumes the form of a fish.”
Uncle George emptied the bottle containing the young trout into a wooden
box which he had made. This box was fifteen inches long, four inches
broad, and four inches deep. The inside of it he had charred with a
red-hot iron after it was put together. It was placed under the tap, and
the water dripped into it all day and all night.
Frank made a small gauze net about the size of a dessert-spoon, and with
this they lifted troutlets out of the box whenever they wanted to
examine them.
As their uncle had said, the creatures changed from day to day. By
placing a single trout in a white saucer, the boys could note these
changes; but they were such lively little creatures that making good
sketches of them was somewhat difficult.
First the big black dots became more like eyes. Then delicate fins and
tail appeared, and mouths which opened and shut. At the top of the
yolk-sac, just under the head, the boys could see a little red thing
like a heart beating constantly. As the yolk-sac grew smaller, the
little fish’s body grew more shapely, and tiny brown spots appeared all
over it.
At last, at the end of six weeks, the yolk was completely gone, and the
young trout were now beautiful little fish, shaped and coloured exactly
like big trout.
Then Uncle George began to feed them. They were fed four times a day on
the yolk of an egg which had been boiled for half an hour. A very small
quantity of this hard yolk was squeezed through a piece of gauze into
the water, and the little fishes dashed at it and gobbled it up
greedily.
They were so rapid in their movements, swimming about and leaping out of
the water, that the boys were never tired of watching them.
“What are the brown spots on a trout for?” Frank asked his uncle one
day.
“The trout is protected by his colour,” said Uncle George. “Each trout
is coloured like the bed of the stream he lives in, and the spots
resemble grains of sand and tiny pebbles. The trout can change his
colour, like the frog, as I will show you.”
Uncle George took two trout out of the box and placed them in a glass
dish. He placed the dish in a white saucer, and so arranged it that
water was kept flowing into and out of it.
Next day he took two more trout out of the box and placed them in the
glass dish. It was then seen that the first two trout had grown quite
light in colour. They were much paler than those taken out of the box,
the inside of which was charred and black.
One day Uncle George found two of the trout dead in the box.
“I am afraid, boys,” he said, “that we cannot keep them confined any
longer. Get a large pail full of water, and we will carry them to the
brook.”
“We must come here and fish next year, Frank,” said Tom, after the trout
were transferred to the brook. “How long will it be before they become
big trout, Uncle George?”
“They are now about an inch long,” said Uncle George. “In a year they
will be four inches long. In about three years, if they are not devoured
by larger trout, they will weigh about a pound apiece.”
“I think it is a shame to kill such pretty little creatures,” said
Frank.
“I quite agree with you, Frank,” said his uncle.
Exercises on Lesson XIII.
1. Compare a newly-hatched trout with a seed (bean). How do they
resemble, and how do they differ from one another?
2. The trout is protected by its colour markings. Make a list of any
other animals you know that are “colour protected.”
3. If you put a fish (trout) into water which has been boiled and
allowed to cool, it dies. What are your reasons for this?
4. Make notes, with sketches, of the development of a young trout from
the time it is hatched until it requires food.