VARIABILITY --(books about variability)--

Darwin and Modern Science by Seward
Darwinism (1889) by Alfred Russel Wallace
Life: Its True Genesis by R. W. Wright
More Letters of Charles Darwin ? Volume 1
On the Genesis of Species by St. George Mivart
On the Origin of Species by Means of Natural Selec
On the origin of species by Charles Darwin
Species and Varieties, Their Origin by Mutation
The Descent of Man by Charles Darwin
On the origin of species by Charles Darwin
Variation of Animals and Plants under Domesticatio
Variation of Animals and Plants under Domesticatio