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One day, a teacher took his pupils to a chicken farm to pay a visit. When they came near the incubator, a chick just got out of its eggshell.

"It's wonderful to see a little thing come our from the eggshell, Isn't it?" the teacher said.

"Yes, sir." said one of the boys, "but it would be more wonderful if we knew that how a chick gets into its eggshell before hand."