Sexing a fancy rat

Question
I cannot tell if my son's fancy rat is a boy or a girl.  It seems to have a litte penis, but it also has an opening right underneath the penis and what looks to be nipples on the sides for nursing.  Please help!  

Answer
Male rats have rather large testicles, provided their old enough.  Rats can be neutered too, though, but if he got him from a pet store that is very unlikely.  If he/she has testicles they are right under the base of the tail - they don't hang but protrude towards the tail.  If you have seen something that looks like a penis, then he is likely a little boy since females don't have anything like that unless something is wrong (such as a prolapsed vagina).  Male rats have nipples just like females, and the other opening you are seeing is most Lilly his anus.

Amanda