So Great Is The Economy Of Nature,

The More I Study Nature, The More I Become Impressed With Ever-increasing Force With The Conclusion, That The Contrivances And Beautiful Adaptations Slowly Acquired Through Each Part Occasionally Varying In A Slight Degree But In Many Ways, With The Preservation Or Natural Selection Of Those Variations Which Are Beneficial To The Organism Under The Complex And Ever-varying Conditions Of Life, Transcend In An Incomparable Degree The Contrivances And Adaptations Which The Most Fertile Imagination Of Man Could Suggest With Unlimited Time At His Disposal.

Among The Scenes Which Are Deeply Impressed On My Mind, None Exceed In Sublimity The Primeval [tropical] Forests, ... Temples Filled With The Varied Productions Of The God Of Nature. No One Can Stand In These Solitudes Unmoved, And Not Feel That There Is More In Man Than The Mere Breath Of His Body.

Extinction Has Only Separated Groups: It Has By No Means Made Them; For If Every Form Which Has Ever Lived On This Earth Were Suddenly To Reappear, Though It Would Be Quite Impossible To Give Definitions By Which Each Group Could Be Distinguished From Other Groups, As All Would Blend Together By Steps As Fine As Those Between The Finest Existing Varieties, Nevertheless A Natural Classification, Or At Least A Natural Arrangement, Would Be Possible.

It's An Awful Stretcher To Believe That A Peacock's Tail Was Thus Formed But ... Most People Just Don't Get It - I Must Be A Very Bad Explainer

The Lower Animals, On The Other Hand, Must Have Their Bodily Structure Modified In Order To Survive Under Greatly Changed Conditions. They Must Be Rendered Stronger, Or Acquire More Effective Teeth Or Claws, In Order To Defend Themselves From New Enemies; Or They Must Be Reduced In Size So As To Escape Detection And Danger. When They Migrate Into A Colder Climate They Must Become Clothed With Thicker Fur, Or Have Their Constitutions Altered. If They Fail To Be Thus Modified, They Will Cease To Exist.