"That striking resemblance, together with the fact that they chose Earth to attack out of all the planets of the Solar System, shows they must have originated on a world much like this. But while on Earth the slime molds are the highest reticular organisms, and the dominant life is all multicellular, on the monsters' home world conditions must have favored unicellular growth. Probably as a result of this unspecialized structure, the monsters have attained their great size and perhaps for the same reason they have achieved what even intelligent cellular life so far hasn't--liberation from existence bound to one world's surface, the conquest of space. They accomplished it not by invention but by adaptation, as brainless life once crawled out of the sea to conquer the dry land. "The monsters who have descended on Earth must represent the end result of a long evolution completed in space itself. They are evidently deep-space beings, able to propel themselves from planet to planet and from star to star in search of food, guided by instinct to suns and worlds like ours. Descending on such a planet, they move across its surface systematically ingesting all edible material--all life not mobile enough to avoid their march. They are like caterpillars that overrun a planet and strip it of its leaves, before moving on to the next. "Man is a highly mobile species, so our direct casualties of this invasion have been very light and will continue to be. But when the monsters have finished with Earth, there will be no vegetation left for man's food, no houses, no cities, none of the fixed installations of civilization, and the end will be far more terrible than if we were all devoured by the monsters." * * * * * Westover awoke, feeling himself bathed by the cold sweat of nightmare--then he realized that a misty rain had wetted his face and sogged his clothes. That, and the sleep he had had, refreshed him and made his mind clearer than it had been for days, and he remembered that he could not sleep but had to go on, searching with a hope that would not die for some miraculously spared refuge where civilization and science might yet exist, where there would be the means to realize his idea for stopping the monsters. He sat up, eyes searching the sky for a sign to tell him how long he had slept. Low on the western horizon he found the faint glow that told of the moon's setting; and in the east a stronger light was already struggling through the clouds and mist, becoming every moment less tenuous and illusory, more the bitter reality of the breaking day.