Darwinism

-Brain development--Local relations of fossil and living animals--Cause of extinction of large animals--Indications of general progress in plants and animals--The progressive development of plants--Possible cause of sudden late appearance of exogens--Geological distribution of insects--Geological succession of vertebrata--Concluding remarks

CHAPTER XIV

FUNDAMENTAL PROBLEMS IN RELATION TO VARIATION AND HEREDITY

Fundamental difficulties and objections--Mr. Herbert Spencer's factors of organic evolution--Disuse and effects of withdrawal of natural selection--Supposed effects of disuse among wild animals--Difficulty as to co-adaptation of parts by variation and selection--Direct action of the environment--The American school of evolutionists--Origin of the feet of the ungulates--Supposed action of animal intelligence--Semper on the direct influence of the environment--Professor Geddes's theory of variation