Importance of variability--Popular ideas regarding
it--Variability of the lower animals--The variability of
insects--Variation among lizards--Variation among
birds--Diagrams of bird-variation--Number of varying
individuals--Variation in the mammalia--Variation in internal
organs--Variations in the skull--Variations in the habits of
animals--The variability of plants--Species which vary
little--Concluding remarks



CHAPTER IV

VARIATION OF DOMESTICATED ANIMALS AND CULTIVATED PLANTS


The facts of variation and artificial selection--Proofs of the
generality of variation--Variations of apples and
melons--Variations of flowers--Variations of domestic
animals--Domestic pigeons--Acclimatisation--Circumstances
favourable to selection by man--Conditions favourable to
variation--Concluding remarks



CHAPTER V

NATURAL SELECTION BY VARIATION AND SURVIVAL OF THE FITTEST