THE VARIABILITY OF SPECIES IN A STATE OF NATURE 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.