Associated systems of electrons, constituting atoms of Matter; and so The whole inorganic Universe. Then, as a new and astonishing departure, comes-- The cell, or protoplasmic complex which Life can construct and utilise for manifestation and development.[33] And after that A brain cell, which can become the physical organ for the rudiments of Mind. Followed by Further mental development until Consciousness becomes possible. With subsequent Sublimation of consciousness into Ethics, Philosophy, and Religion. We need not insist on these or any other stages for our present purpose; yet something of the kind would seem to have occurred, in the mysterious course of time. THREE EXPLANATORY NOTES NOTE A.--MECHANICS OF JUMPING BEAN The biological explanation of a jumping bean is sometimes felt to be puzzling, inasmuch as the creature is wholly enclosed; and a man in a boat knows that he cannot propel it by movement inside, without touching the water or something external. But the reaction of a table can be made use of through the envelope, and a live thing can momentarily vary its own weight-pressure and even reverse its sign. This fact has a bearing on some psycho-physical experiments, and hence is worthy of a moment's attention. To weigh an animal that jumps and will not keep still is always troublesome. It cannot alter its average weight, truly, but it can redistribute it in time; at moments its apparent weight may be excessive, and at other moments zero or even negative, as during the middle of an energetic leap. Parenthetically we may here interpolate a remark and say that what is called interference of light (two lights producing darkness, in popular language) is a redistribution of luminous energy in space. No light, nor any kind of wave motion, is destroyed by interference when two sets of waves overlap, but the energy rises to a maximum in some places, and in other places sinks to zero. No wave energy is consumed by interference--only rearranged. This fact is often misstated. And probably the other statement, about the varying apparent weight--_i.e._ pressure on the ground--of a live animal, may be misstated too: though there is no question of energy about that, but only of force. The force or true weight, in the sense of the earth's attraction, is there all the time, and is constant; but the pressure on the ground, or the force needed to counteract the weight, is not constant. After momentary violence, as in throwing, no support need be supplied for several seconds; and, like the maggot inside a hollow bean, a live thing turning itself into a projectile may even carry something else up too. It is instructive also to consider a flying bird, and a dirigible balloon, and to ask where the still existing weight of these things can be found. NOTE B.--DIFFERENCES BETWEEN A GROWING ORGANISM AND A GROWING CRYSTAL