Charles Darwin,
The Variation of Animals and Plants under Domestication…
“ The Carnivora, with the exception of the Plantigrade division, breed (though with capricious exceptions) about half as freely as ruminants. Many species of Felidae have bred in various menageries, although imported from diverse climates and closely confined. Mr. Bartlett, the present superintendent of the Zoological Gardens (18/17. On the Breeding of the Larger Felidae 'Proc. Zoolog. Soc.' 1861 page 140.) remarks that the lion appears to breed more frequently and to bring forth more young at a birth than any other species of the family. ”
