INDEX.

Picidæ, sexual colouring and nidification of, 242.
Pipridæ, sexual colouring and nidification of, 245.
Pittidæ, 253.
Pliocerus equalis, 101; P. elapoides, P. euryzonus, 102.
Pæciloderma terminale, 93.
Polarity, Forbes’ theory of, 17, 45.
Polymorphism, 145; illustration of, 157.
Population of species, law of, 28; does not permanently increase, 29; not determined by abundance of offspring, 29; checks to, 30; difference in the case of cats and rabbits explained, 32.
Prevision, a case of, 122.
Prioniturus, 196.
Protection, various modes in which animals obtain it, 69-71, 258; greater need of, in female insects and birds, 113.
Protective colouring, theory of, 65.
Psittaci (Parrots), sexual colouring and nidification of, 242.
Pterosauria, 298.
Ptychoderes, 94.
RACES, or subspecies, 160; of man, origin of, 319.
Redbreast and woodpigeon, protective colouring of, 53, 54.
Representative groups, 9; of Trogons, butterflies, &c., 12.
Reptiles, protective colouring of, 54.
Rhamphastidæ, sexual colouring and nidification of, 242.
Rhinoceros, 299.

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