Editor Mort Weisinger's recycling of ideas on the Superman feature is notorious: stories were rewritten after the passing of a few years, scripts from the TV show were adapted into the comic books, and even cover scenes from pulps that Weisinger had worked on turned up on the comics' covers.
"Each of these big creatures appeared to be composed of small, living fleshy pink cubes. Each cube was four inches square, and had two twinkling bright eyes and a small mouth-opening.
"'Why, I never saw anything like these before,' Captain Future muttered, stepping forward. (...)
"But now, as Captain Future approached, the centipede creatures underwent an incredible transformation.
"Their big, geometrical bodies disintegrated. They broke up into the scores of living cubes of which they were composed. Each cube was revealed to be a separate, tiny living creature. Each had eight tiny claws or legs, one at each corner of its cubical body, as well as its own eyes and mouth and ears.
"These hundreds of cube-creatures scurried swiftly together, and joined into a single big figure. The living cubes joined tightly, each to the next, by instantly hooking their tiny claws together.
"Silently and quickly as though by magic, the cubical creatures had combined to form a towering, semi-human figure ten feet high. It advanced on square, stocky legs with its massive arms raised menacingly toward the Futuremen."
Here's a scene (drawn by George Papp) from "The Super-Planet of Clark Kent and Lana Lang," the Superboy story in Adventure Comics 300 (Sept/63):
In this case, the sequence goes from monster to centipede creature. I read this story when it came out, and remembered this vividly ever since; it was decades later that I reread it and attributed the script to Edmond Hamilton from the writing style. A few years after that, I read the Captain Future novel by Hamilton and instantly recognized the Cubicals, as he calls them there.