I thought I'd write how dissecting tools and manuals could be obtained inexpensively. Here are a few suggestions where you might find one. Half-price bookstores may carry Biology lab manuals. Hope these suggestions help.
Earthworms are annelids meaning segmented.
That's why they have so many lines running across their bodies. Make sure you have the dark side facing down on your dissecting tray. These are to keep the side walls pinned open. Rather aortic arches. Use a styrofoam plate or trays that meat or fruit are packed on.