_Illustration of the differentiation of the whole animal kingdom_ --Development of eggs of all kinds of animals--This a type of changes in Phylogeny--Why Ontogeny repeats Phylogeny-- Law of acceleration 176 _Proofs from rudimentary and useless organs_--Examples from whale: Teeth--Limbs--Hair--Olfactive organs--Examples from man: muscles, cæcal appendage--Significance of useless organs 179 CHAPTER VIII. PROOFS FROM GEOGRAPHICAL DISTRIBUTION OF ORGANISMS. _Geographical faunas and floras_--Conditions which limit 183 _Temperature-regions_--Illustrated by plants--In latitude and in elevation--Same in animal species 184 _More perfect definition of regions_--Range of different Taxonomic groups--Gradual shadings on borders of range-- Shadings out of individuals in number and vigor, but not in specific character--As if centers of origin--Effect of east and west barriers--Temperature regions repeated south of the equator, but not species--As if centers of origin 186 _Continental faunas and floras_--Temperature zones continuous, but not species--Reason: ocean barriers--As if centers of origin--Polar regions: one. Why--Temperate zone-- Different species in different continents--Species of United States and of Europe almost wholly different--As if origin local--Exceptions--(1) Introduced species--(2) Hardy or else wide-migrating species--(3) Alpine species--Tropical zone of two continents still more different--Same true of south temperate zone 188 _Subdivisions of continental faunas and floras_--Illustrated by fauna and flora of United States 191 _Special Cases_--Australia--Madagascar--Galapagos--River mussels 192 _Marine species_--Same principles applicable--Therefore organic forms grouped in regions, sub-regions, provinces, etc.-- Primary regions according to Wallace--According to Allen 192 _Theory of the origin of geographical diversity_--Specific centers of creation--Objections to. The element of time left out--Progressive change in unlimited time, or evolution the only rational explanation--This connects with geographical changes in geological times, especially the Glacial epoch-- Geographical diversity in other times 193