"Are there any people in Mars?" she asked.
"People down here say that there aren't. A man told me the other day that he knew this for a fact. On the other hand, people in Mars know for a fact that there isn't anybody on the Earth. Probably they are both wrong."
"I should like to know a lot about things," sighed Celia. "Do you know anything about limpets?"
"Only that they stick like billy-o."
"I suppose more about them is known than that?"
"I suppose so. By people who have made a specialty of them. For one who has preferred to amass general knowledge rather than to specialize, it is considered enough to know that they stick like billy-o."
"You haven't specialized in anything, have you?"
"Only in wives."
Celia smiled and went on. "How do you make a specialty of limpets?"
"Well, I suppose you—er—study them. You sit down and—and watch them. Probably after dark they get up and do something. And of course, in any case, you can always dissect one and see what he's had for breakfast. One way and another you get to know things about them."