In short, the animal and vegetable lines, diverging widely above, join below in a loop.

The former conviction that these two kingdoms were wholly different in structure, in function, and in kind of life, was not seriously disturbed by the difficulties which the naturalist encountered when he undertook to define them.

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.

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.

The best opinion now is, that there are multitudinous forms which are not sufficiently differentiated to be distinctively either plant or animal, while, as respects ordinary plants and animals, the difficulty of laying down a definition has become far greater than ever before.

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.

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.