$(document).ready(function() {
    $('.slideshow').each(function() {
        var $this = $(this);
        $this.cycle({
            speed:    300,
            timeout:  0,          
            fx:       'fade',
            
            // use slideshow as the transition trigger
            next: $this.closest('div.portfolio_gallery').find('.next'),
            prev: $this.closest('div.portfolio_gallery').find('.prev')
        });
    });
});