Gender differences

We are getting ready to find out the gender of the new baby, and John is very excited! We told him there is a special camera to look inside my belly to see if it's a boy or a girl. Being a boy, he didn't need to be told what we would be looking for on a boy, he figured that one out himself and mentioned it casually. But then he went on to say "I don't think it's a girl, Mommy. When you showed me the picture of the baby in your tummy [12-week ultrasound], I didn't see any ponytails on the baby."