Since Arisia was Earth-like in composition, atmosphere, and climate, the Arisians were at that time distinctly humanoid. The Eddorians were not. Eddore was and is large and dense; its liquid a poisonous, sludgy syrup; its atmosphere a foul and corrosive fog. Eddore was and is unique; so different from any other world of either galaxy that its very existence was inexplicable until its own records revealed the fact that it did not originate in normal space-time at all, but came to our universe from some alien and horribly different other. As differed the planets, so differed the peoples. The Arisians went through the usual stages of savagery and barbarism on the way to Civilization. The Age of Stone. The Ages of Bronze, of Iron, of Steel, and of Electricity. Indeed, it is probable that it is because the Arisians went through these various stages that all subsequent Civilizations have done so, since the spores which burgeoned into life upon the cooling surfaces of all the planets of the commingling galaxies were Arisian, not Eddorian, in origin. Eddorian spores, while undoubtedly present, must have been so alien that they could not develop in any one of the environments, widely variant although they are, existing naturally or coming naturally into being in normal space and time. The Arisians--especially after atomic energy freed them from physical labor--devoted themselves more and ever more intensively to the exploration of the limitless possibilities of the mind. Even before the Coalescence, then, the Arisians had need neither of space-ships nor of telescopes. By power of mind alone they watched the lenticular aggregation of stars which was much later to be known to Tellurian astronomers as Lundmark's Nebula approach their own galaxy. They observed attentively and minutely and with high elation the occurrence of mathematical impossibility; for the chance of two galaxies ever meeting in direct, central, equatorial-plane impact and of passing completely through each other is an infinitesimal of such a high order as to be, even mathematically, practically indistinguishable from zero. They observed the birth of numberless planets, recording minutely in their perfect memories every detail of everything that happened; in the hope that, as ages passed, either they or their descendants would be able to develop a symbology and a methodology capable of explaining the then inexplicable phenomenon. Carefree, busy, absorbedly intent, the Arisian mentalities roamed throughout space--until one of them struck an Eddorian mind. * * * * *