Answer:
As the new cat was liked by the wife, his fate or condition may be a bit different than that of Pluto, who the wife likens to the devil. Moreover, the narrator's guilt in killing Pluto may also play a part in his desire to not repeat the same monstrosity to the new animal.
Explanation:
Edgar Allen Poe's short story "The Black Cat" revolves around the story of how the unnamed narrator ended up as a death row prisoner. The short story illustrates how a person's mind can be the strongest influencer of one's character, even capable of bringing destruction.
The narrator had just killed his cat, Pluto out of anger which, he admits, he regretted the next day. And in his desire to get a replacement for the dead cat, he got a new one of almost the same appearance. He reveals "It was a black cat -- a very large one -- fully as large as Pluto, and closely resembling him in every respect but one. Pluto had not a white hair upon any portion of his body; but this cat had a large, although indefinite splotch of white, covering nearly the whole region of the breast." He also stated that the cat "purred" and "appeared delighted" to be with him, and in the end, both went home together.
But considering how the two got acquainted with each other, it seems like the same story all over again. The narrator will shower the new animal with love and attention, and the cat reciprocating the actions with its language. But what is different this time is that the wife liked the new cat while she did not like Pluto. This difference may become an important element in the later scenes.