Natural selection is not the wind which propels the vessel, but the rudder which, by friction, now on this side and now on that, shapes the course.
Asa GrayMany years ago it was taught that plants and animals were composed of different materials: plants, of a chemical substance of three elements,- carbon, hydrogen, and oxygen; animals of one of four elements, nitrogen being added to the other three.
Asa GrayIndeed upon much that may have to say, I expect rather the charitable judgment than the full assent of those whose approbation I could most wish to win.
Asa Gray