Form with two inputs not submitting?

Could someone please explain why this code isn't working:

$('form').on('submit', function (e) {
    e.preventDefault();

    var first = $('.first').val();
    var next = $(".next").val();
    alert(first + " " + next);
});

http://ift.tt/1AqvMct

It seems to work fine when I remove one of the two inputs but having them both there messes it up.