Musar for Niddah 45:63

מתקיים אמר רב ירמיה מדפתי

that it is viable! But did not Rab Judah citing Rab state: R. Meir gave his ruling<span class="x" onmousemove="('comment',' That an abortion of a beast or wild animal is regarded as a valid birth. ');">⁵¹</span> only because in the case of its own species<span class="x" onmousemove="('comment',' Beast born from beast or wild animal from wild animal. ');">⁵²</span> it is viable?<span class="x" onmousemove="('comment',' But not when a woman aborted such creatures. The question of wife's sisters, consequently, could never arise in such a case. What then was the point in R. Jeremiah's peculiar enquiry? ');">⁵³</span> Said R. Aha b. Jacob: 'To such an extent did R. Jeremiah try<span class="x" onmousemove="('comment',' By his absurd enquiries. ');">⁵⁴</span> to make R. Zera laugh; but the latter did not laugh'.<span class="x" onmousemove="('comment',' It is forbidden to indulge in laughter in this world (cf. Ber. 31a). ');">⁵⁵</span> [Reverting to] the [previous] text, 'Rab Judah citing Rab stated: R. Meir gave his ruling only because in the case of its own species it is viable.' Said R. Jeremiah of Difti:

Orchot Tzadikim