Ascidians, placental structure, [81].
Assumptions of Mr. Darwin, [16].
Astronomical objections, [136].
Auditory organ, [74].
Augustin, St., [17], [263], [264].
Aurelius, Marcus, [206].
Avian limb, [106].
Avicularia, [80].
Axolotl, [165].
Aye-Aye, [107].