A crab of mature age and experience is represented by an ancient writer as offering advice to his son somewhat in these terms: “My son, I have observed in you a most regrettable tendency to walk with ungraceful and unbecoming sidelong steps. Pray endeavour to conquer this pernicious habit and to adopt a straightforward and direct mode of progression.”Excellent advice! Though the gait of the existing generation of crabs leads one to fear that it failed to take effect.