At the close he glances briefly at the difficulties the theory presents. We must regard even the first beginnings of life as the outcome of “evolution.” Naturally. Darwin’s God has no use for this prophet. But how shall we conceive it? Was the thing that first developed from the inorganic “a simple cell, such a being as those that now exist in such numbers as independent beings on the ambiguous frontier of the animal and vegetal worlds?” Or was it a particle of plasm merely, “like certain amœboid organisms that do not seem to have attained yet the organisation of a cell”? Again the simple question contained a whole programme. Schleiden had first shown in 1838 that the body of any plant can be dissolved into tiny living corpuscles, which he called “cells,” because they often had the appearance of a filled honeycomb. A year later Schwann proved, in Johannes Müller’s laboratory, that the higher animal also is a product of these cells. The cell was recognised as the living unit that composed the oak and the rose, the elephant and the worm. Man himself, in fine, was but a pyramid of these cells—or, to speak more accurately (as each cell has its own life), an immense community of cells, a cell-state. Virchow had, as we saw, laid the greatest stress on this last and most important deduction from the cell-theory a short time before. He looked upon every individual man as a mysterious plurality—a plurality of cells. Pathology, the science of disease, must take account of this. Health was the harmonious co-operation of the cell-state; disease was the falling-away of some of the cells to special work that injured or destroyed the whole community. This conception had inaugurated a new epoch in medicine, making it a consciously ministering art in the service of the living human natural organism. The Darwinian had now the task of showing the validity of this conception in his own province. The genealogical tree of the animals and plants must at once be drawn up in the form of a genealogical tree of the cell. The cells had combined to form higher and higher communities, and each higher species of animal or plant was in reality one of these social constructions. But this complexity was only found in the upper branches. The lower we descend, the simpler we find organisms. The lowest forms of life represent cruder, simpler, and more primitive cell-structures. And the final conclusion was that all the cell-communities or states must have been evolved from unattached individuals whose whole body consisted of a single cell. We cannot strictly call these lowest forms of life either animals or plants; they can only be likened to the single cell. Though Haeckel himself did not know it at the time, all his pretty radiolaria at Messina belonged to this category. The whole swarm of bacilli and bacteria fell into this world of the “unicellulars.” Haeckel’s words threw a brilliant light on the question. Not only the simplest forms of