"It is a widely received notion that the energies of living matter have a tendency to decline and finally disappear, and that the death of the body as a whole is a necessary correlate of its life. That all living beings sooner or later perish needs no demonstration, but it would be difficult to find satisfactory grounds for the belief that they needs must do so. The analogy of a machine, that sooner or later must be brought to a standstill by the wear and tear of its parts, does not hold, inasmuch as the animal mechanism is continually renewed and repaired; and though it is true that individual components of the body are constantly dying, yet their places are taken by vigorous successors. A city remains notwithstanding the constant death-rate of its inhabitants; and such an organism as a crayfish is only a corporate unity, made up of innumerable partially independent individualities."--_The Crayfish_, p. 127. Surely the theory which I have indicated above makes the reason plain why no organism can permanently outlive its experience of past lives. The death of such a body corporate as the crayfish is due to the social condition becoming more complex than there is memory of past experience to deal with. Hence social disruption, insubordination, and decay. The crayfish dies as a state dies, and all states that we have heard of die sooner or later. There are some savages who have not yet arrived at the conception that death is the necessary end of all living beings, and who consider even the gentlest death from old age as violent and abnormal; so Professor Huxley seems to find a difficulty in seeing that though a city commonly outlives many generations of its citizens, yet cities and states are in the end no less mortal than individuals. "The _city_," he says, "remains." Yes, but not for ever. When Professor Huxley can find a city that will last for ever, he may wonder that a crayfish does not last for ever. I have already here and elsewhere said all that I can yet bring forward in support of Professor Hering's theory; it now remains for me to meet the most troublesome objection to it that I have been able to think of--an objection which I had before me when I wrote Life and Habit, but which then as now I believe to be unsound. Seeing, however, that a plausible case can be made out for it, I will state it and refute it here. When I say refute it, I do not mean that I shall have done with it--for it is plain that it opens up a vaster question in the relations between the so- called organic and inorganic worlds--but that I will refute the supposition that it any way militates against Professor Hering's theory.