Part 17

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.

XIV.—SILKWORMS.

The silkworm eggs came in a very small box. They were sent by a friend of Uncle George’s who lived in the south of England. The eggs were stuck to pieces of paper in scattered groups. Some pieces of paper had only one or two eggs on them, others had as many as forty. They were small, round things, flattened on the top, and coloured light green. They reminded the boys of small mustard seeds, but they were not so round.

In answer to Frank’s question as to why the eggs were laid in irregular groups, Uncle George answered:

“When the silk-moth emerges from her pupa case, she lays her eggs anywhere on the floor of her cage. As the eggs are coated with a gluey material when newly laid, they stick firmly to the floor.

“Those people who rear silkworms always have a sheet of clean paper covering the floor of the cage before egg-laying commences. After the eggs are laid, they are found adhering to this sheet of paper. The paper is taken out of the larva cage, and those parts containing eggs are cut out with scissors.”

“How many eggs are laid by one moth,” Frank asked.

“From four to five hundred,” his uncle replied. “Let us get our larva cage cleaned out, and we will put these eggs in the lower part of it and await their hatching.”

“Why in the lower part,” Frank asked, as he set about cleaning the cage.

“Because its floor is a drawer which can be pulled out. If you put them in the upper part, you must lay a sheet of paper on the floor first, for your silkworms must not be handled on any account.”

“And how long do we have to wait for these eggs to hatch?” asked Tom.