O
Odor as protection, [117].
Opossum playing dead, [107].
Origin of birds, [181].
feathers, [102].
flight, [122].
hair, [102].
life, [159].
lungs, [177].
milk glands, [212].
placenta, [210].
variations, [50].
"Origin of Species" published, [41].
Orthogenesis and Eimer, [243].
Oxford meeting of British Association, [41].