The tone of the "The Egg" is humorous and jaded. In fact, the tone might be summed up in the narrator's comments below as he bemoans, as if he is a philosopher himself, how eggs become chickens, have brief, disease-prone lives, then reproduce themselves and die:
It [a chicken] is born out of an egg, lives for a few weeks as a tiny fluffy thing such as you will see pictured on Easter cards, then becomes hideously naked, eats quantities of corn and meal bought by the sweat of your father's brow, gets diseases called pip, cholera, and other names, stands looking with stupid eyes at the sun, becomes sick and dies. ... Most philosophers must have been raised on chicken farms. One hopes for so much from a chicken and is so dreadfully disillusioned.
This tone is sustained throughout because most of the story is an overview of the narrator's parents' lives, as understood by their son. It is his weary voice that dominates the text. Only near the end do we get to hear a few snippets of any voice other than the narrator's.
Near the end of the story, the family moves to the humorously named Pickleville to open a restaurant after their failure to thrive as chicken farmers. It is only when his father, a decidedly dour man in his son's eyes, decides the restaurant should be lively and entertaining, that we get to hear his less-than-entertaining speech:
"They want some place to go. I tell you they want some place to go," he said over and over.
Some time later, the narrator zooms in on a particular scene, in which his father, trying to be friendly and upbeat with a Joe Kane who comes in, begins to chat with him about Christopher Columbus, only to fail dramatically to bring a sense of joy and gaiety into his restaurant:
"Well," he began hesitatingly, "well, you have heard of Christopher Columbus, eh?" He seemed to be angry. "That Christopher Columbus was a cheat," he declared emphatically.
The humor comes from the juxtaposition of the narrator's high philosophizing about life in a dry, cynical way with the very ordinariness of his parent's largely failed existences as chicken farmers and restaurant owners.