and differently conditioned as to the environment, would develop on divergent lines of evolution.
The conclusion, deductively arrived at, that the conditions under which life has existed and still exists, are such that evolution must have occurred and still occurs, is therefore decisively confirmed by the conclusion, inductively arrived at, that evolution certainly has occurred, and therefore, though in the subsequent pages of this work many proofs will incidentally be afforded of the actuality of Organic Evolution, in future it will be assumed that the truth of it is admitted, and we shall endeavour only to fill in the details of the map as to the fidelity of the outlines of which no well-informed man any longer entertains a doubt.
The upward march of life from the earliest beginnings may be compared to that of a horde of men, leaving their old habitations and entering new lands; travelling ever forwards, but ever sending out branch swarms that part from the parent horde, never to reunite with it, and ever leaving some of their members behind on the way, some of whom may journey backwards; such hordes as those which in ancient times came from the East, settled the countries they passed over, sent offshoots to the North and South, and rolled on the tide of conquest till they destroyed the old Roman Empire. The lowest, or in other words the least differentiated and specialized forms of life, may be compared to those members of the horde that stayed behind in the original habitat, the intermediate forms to those that halted and settled by the way, and the highest forms to those that journeyed till they reached the farthest limits of the wanderings. The comparison is made yet closer if we imagine, as generally true of life, that which is generally true of emigrant swarms of men, namely, that those that stayed in the original habitat, that those that halted, diverged, or
