Homologue. The Same Organ In Different Animals

That The Variability Of An Organism To A Certain Extent Is A Constant And Certain Condition Of Life We Admit, Otherwise There Would Be No Distinguishable Individuals Of A Species.

Analogue. A Part Or Organ In One Animal Which Has The Same Function As Another Part Or Organ In A Different Animal.

The Laws Of Coexistence;-the Adaptation Of Structure To Function; And To A Certain Extent The Elucidation Of Natural Affinities May Be Legitimately Founded Upon The Examination Of Fully Developed Species;-but To Obtain An Insight Into The Laws Of Development,-the Signification Or Bedeutung, Of The Parts Of An Animal Body Demands A Patient Examination Of The Successive Stages Of Their Development, In Every Group Of Animals.

The Powers, Aspirations, And Mission Of Man Are Such As To Raise The Study Of His Origin And Nature, Inevitably And By The Very Necessity Of The Case, From The Mere Physiological To The Psychological Stage Of Scientific Operations.

Mr. Darwin Contributes Some Striking And Ingenious Instances Of The Way In Which The Principle Partially Affects The Chain, Or Rather Network Of Life, Even To The Total Obliteration Of Certain Meshes.