OP... yes, odds are it is a male, but like it has been said it could just be a small female.
The rest of you...
I just spent a lovely evening popping and probing babies, getting peed all over. One even managed to squirt half way across the table and pee in my beer. That one will be named party pooper if i keep it.
Anyway, there is no way to be certain with any visual inspection method. We actually bet on them at my house. This year no one has been extraordinarily accurate.