What are the essential differences between Henry Jekyll and Edward Hyde? Is Jekyll purely "good" and Hyde purely "evil"? Do they share any traits—in other words, does some of Jekyll remain within Hyde?

Although presented as a scientific experiment, Jekyll undertook this task to allow himself a release from the respectable guise of Victorian sensibilities. Hyde is a small, deformed, disgusting man somewhat younger than Dr. Jekyll who is apparently devoid of a profession. Lanyon, Utterson and Enfield all describe witnessing something indefinably evil and horrific in Edward Hyde's face. He is often compared to animals, implying that he is not a fully evolved human being. Despite these descriptions, Hyde is generally civilized in his interactions with others, most notably Utterson and Lanyon. Dr. Jekyll describes Hyde as "pure evil," who menaces society at night, trampling a girl in the street and murdering Sir Danvers Carew. We learn at the end of the story that Edward Hyde and Dr. Henry Jekyll are in fact the same person. The dark and the light are battling within Jekyll, two polar opposites of good vs evil, rather than balancing each other out.