Reference for Bava Kamma 160:7
והא מעשה דרב אוכמא הוה התם אוכמא בר חיורא הוה והא מבעיא בעיא ליה רבינא
of the cat [where it was found dead]. An objection was raised [from the following]: R. Simeon b. Eleazar says: It is permissible to breed village dogs, cats, apes and porcupines, as these help to keep the house clean. [Does this not prove that it is permissible to breed cats?] — There is, however, no contradiction, as the latter teaching refers to black cats, whereas the former deals with white ones.<span class="x" onmousemove="('comment',' Which constitute a danger. ');"><sup>11</sup></span> But was not the mischief in the case of Rab done by a black cat? — In that case it was indeed a black cat, but it was the offspring of a white one. But is not this the very case about which Rabina raised a question? For Rabina asked: What should be the law in the case of a black cat which is the offspring of a white one? — The problem raised by Rabina was where the black was the offspring of a white one which was in its turn a descendant of a black cat, whereas the accident in the case of Rab occurred through a black cat which was the offspring of a white one that was similarly the offspring of a white cat.