It's not possible to positively ID the plant the slugs have been dining on.  But the damage is not only ugly to look at, it threatens the life of the plant since the leaves make the plants food.  Some interesting methods of protecting plants from slug invasions have been discussed on the site.  We've all heard of using beer, salt, and some other stuff you may have around the  house.  The one that impressed me the most was to place copper around the plant being attacked.  When the slugs crawl across the copper, it's shocks and kills them.  Using copper wire is easy.  Just lay it around the plant, and bend the ends so they can be pushed into the soil to hold wire in place.  I'll be going out later to see if copper wire is working on the little beasties.  That was a simple procedure to set up, so let's hope it works.