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.

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.

This view, as a rounded whole and in all its essential elements, has very recently disappeared from science. It died a royal death with Agassiz.

It was implicitly supposed that every living thing was distinctively plant or animal; that there were real and profound differences between the two, if only they could be seized.

Many 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.

We have spoken of beings so low in the scale that the individuals throughout their whole existence are not sufficiently specialized to be distinctively plant or animal: yet these are definite life in simpler shape.

Next it was found that it was physiologically and structurally the same in the plant, that it was the living part of the plant, that which manifested the life and did the work in vegetable as well as in animal organisms.