Read it through once

“This wonderful creature dates back like the kangaroo and many other Australian hydrocephalous invertebrates, to an age long anterior to the advent of man upon the earth; they date back, indeed, to a time when a causeway hundreds of miles wide, and thousands of miles long, joined Australia to Africa, and the animals of the two countries were alike, and all belonged to that remote geological epoch known to science as the Old Red Grindstone Post-Pleosaurian. Later the causeway sank under the sea; subterranean convulsions lifted the African continent a thousand feet higher than it was before, but Australia kept her old level. In Africa's new climate the animals necessarily began to develop and shade off into new forms and families and species, but the animals of Australia as necessarily remained stationary, and have so remained until this day. In the course of some millions of years the African Ornithorhynchus developed and developed and developed, and sluffed off detail after detail of its make-up until at last the creature became wholly disintegrated and scattered. Whenever you see a bird or a beast or a seal or an otter in Africa you know that he is merely a sorry surviving fragment of that sublime original of whom I have been speaking—that creature which was everything in general and nothing in particular—the opulently endowed 'e pluribus unum' of the animal world.