Read it through once

"Now, then," said Wilson, "I have here the natal autographs of two children--thrown up to ten times the natural size by the pantograph, so that any one who can see at all can tell the markings apart at a glance. We will call the children A and B. Here are A's finger-marks, taken at the age of five months. Here they are again, taken at seven months. [Tom started.] They are alike, you see. Here are B's at five months, and also at seven months. They, too, exactly copy each other, but the patterns are quite different from A's, you observe. I shall refer to these again presently, but we will turn them face down, now.