It may be convenient here to explain certain facts regarding the Dwellers of which I learnt later, and in gradual ways. They had, in the course of numerous millenniums, developed bodies which were immune from disease, and (in comparison with our own) from accidental injury also. So far as their experience showed, there was no physical deterioration, nor any reason why they should not continue indefinitely. Yet their solution of the problem of longevity proved inferior to that which had been evolved by the Amphibians, in an unforeseen way. In our own race, we know that the desire of life may persist in a body which is both old and organically defective, and that the brain is usually the last stronghold of a vitality which is reluctantly surrendered. Their experience was opposite. A time would come when the body functioned, but the mind grew weary. Year by year, an increasing lethargy would be succeeded by a more active desire for death, till the slow operation of their own will-power would destroy their bodies through the misery of its final centuries. To the young, this condition would appear incredible, and they would confidently boast that they would resist it successfully, but, sooner or later, it would inevitably descend upon them. Such was their individual doom: as a race they lived under a darker shadow. When it became evident that they had so far overcome the threats of disease and decay that the individual might continue indefinitely, they had naturally been concerned rather by the fear that there might be an ultimate congestion of population, than that the race should fail in fecundity. But this fear had not been acute, because they were then engaged in exploiting a new, and seemingly almost limitless, subterranean territory. Also, they passed through a period of warfare with the inhuman population of other portions of the earth’s surface, in the course of which many of them were destroyed, and which remained as a continuing menace when the actual conflict ceased.