Does the story have a protagonist? Does the story have an antagonist? If so, who?

One could argue that Mr. White is the protagonist in W. W. Jacobs's short story "The Monkey's Paw." Mr. White could be considered the protagonist because he is the leading character and central figure, who makes all three wishes using the magic monkey's paw, and Jacobs primarily focuses on his thoughts and emotions more than any other character in the story. After having an ominous, unnerving conversation with Sergeant-Major Morris regarding the monkey's paw, Mr. White saves the talisman from the fire and proceeds to wish for two hundred pounds to pay off his mortgage. Mr. White not only brings up the topic of the monkey's paw, but he also saves it from the fire and makes the first wish, which sets in motion the chaotic chain of events that results in his son returning from the grave. After the Whites lose their son, Mr. White is apprehensive about making the second wish for Herbert to return and frantically locates the paw to make a third wish just in the nick of time. Overall, Mr. White is considered the protagonist of the short story because he is the central character and leading figure, who sets in motion the chain of events and saves his wife from witnessing their zombie-like son when she opens the door at the end of the story.

In "The Monkey's Paw," the protagonist (or the leading character) is Mr. White. He is the protagonist because it is his friend, Sergeant-Major Morris, who brings the monkey's paw into the family home. Moreover, it is Mr. White who makes the first wish, setting in motion the plot's chain of events.
The antagonist, the person who opposes the protagonist, could arguably be the sergeant-major because he gives the monkey's paw to the family even though he knows that it possesses a very dark form of magic.
However, it could also be argued that Mrs. White plays the role of antagonist because, at the end of the story, she uses the monkey's paw to bring back her son, Herbert, even though Mr. White tells her that it is a "foolish" and "wicked" thing to do. 
Through Mrs. White's actions at the end of the story, Mr. White's status as the protagonist is confirmed. He uses his third wish to wish Herbert away, thereby overcoming the evil powers of the monkey's paw.