On account of the technical limitations of the short story the number of characters which may have principal or "speaking" parts is very small--in general only two, and frequently but one. There are usually other characters present to help out the action, but they are merely supernumeraries, without form, life or influence. There are many violations of this rule, I admit, among them such stories as Hawthorne's "The Great Stone Face," "The Seven Vagabonds," and "The Great Carbuncle;" but analysis shows them to be panoramic or episodic in effect, and really violating the unity of action which the short story demands. For similar reasons the characters presented must be unnaturally isolated, with little past and less future, and most strangely lacking in relatives; for the few thousand words of the short story permit but a cursory treatment of the ancestry, birth, breeding and family of the one or two important characters. If by any trick they can be made the last of a long line, and be snatched from obscurity into the momentary glare of the lime light, so much the better for author, reader and character; but if some portion of their history bears upon the story, let it be presented by subtle touches, preferably by references in the dialogue, so that the reader obtains the necessary knowledge without being conscious of the means.
The few real characters in the story must be made unusually interesting on account of their loneliness. They compose the story, they represent the human race, and if they fail us we are in sad straits. They must be individual; they must stand out sharply from the page, clear and attractive, and leave no doubt of their personalities. More than any other form of fiction, the short story depends upon its hero and heroine, who have "star parts" and monopolize the stage of action. We must see them so vividly that when they speak and act we shall perceive them as actual personages. It is such accuracy of depiction that makes Rip Van Winkle, Sherlock Holmes, Van Bibber, and a host of others enter into our thoughts and speech as if they had really lived.