This substance, which is manifold in its forms and protean in its transformations, has, in its state of living matter, one physiological name which has become familiar, that of protoplasm.

Your candor is worth everything to your cause. It is refreshing to find a person with a new theory who frankly confesses that he finds difficulties, insurmountable, at least for the present.

Indeed 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.

I am sufficiently convinced already that the members of a profession know their own calling better than anyone else can know it.

I accept extinction as best explaining disjoined species. I see that the same cause must have reduced many species of great range to small, and that it may have reduced large genera to so small, and of families.

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.

We may take it to be the accepted idea that the Mosaic books were not handed down to us for our instruction in scientific knowledge, and that it is our duty to ground our scientific beliefs upon observation and inference, unmixed with considerations of a different order.