Instructions for a traditional laboratory experiment to record action potentials from giant axons in the earthworm nerve cord. Electrical stimulation at one end of the worm, while recording from the nerve cord at the middle, shows the effect of reaching threshold and allows calculating the speed of conduction. The stimulus strength-duration curve is also measured. The exercise is part of an online lab manual for an undergraduate neurophysiology course: http://www.science.smith.edu/departments/NeuroSci/courses/bio330/labs.html. Each exercise has a video demonstrating the procedure, written instructions, and color images showing details.