Rivalry, in singing, between male birds.
River-hog, African, tusks and knobs of the.
Rivers, analogy of, to islands.
Roach, brightness of the male during breeding-season.
Robbery, of strangers, considered honourable.
Robertson, Mr., remarks on the development of the horns in the roebuck and red deer.
Robin, pugnacity of the male; autumn song of the; female singing of the; attacking other birds with red in their plumage; young of the.
Robinet, on the difference of size of the male and female cocoons of the silk-moth.
Rodents, uterus in the; absence of secondary sexual characters in; sexual differences in the colours of.
Roe, winter changes of the.