"Turn on the rays!" came the brain's thought-order again.
"The end of the road — the last mutation," I panted. "We've got to see — to see—" I drove the switch home.
The rays flashed down again to hide the great gray brain in the cube. Dutton's eyes were staring fixedly, he was clinging to me.
The minutes passed! Each tick of the watch in my hand was the mighty note of a great tolling bell in my ears.
An inability to move seemed gripping me. The hand of my watch was approaching the minute for which I waited, yet I could not raise my hand toward the switch!
Then as the hand reached the appointed minute I broke from my immobility and in a sheer frenzy of sudden strength pulled open the switch, rushed forward with Dutton to the cube's very edge!
The great gray brain that had been inside it was gone. There lay on the cube's floor instead of it a quite shapeless mass of clear, jelly-like matter. It was quite motionless save for a slight quivering. My shaking hand went forth to touch it, and then it was that I screamed, such a scream as all the tortures of hell's crudest fiends could not have wrung from a human throat.
The mass inside the cube was a mass of simple protoplasm! This then was the end of man's evolution-road, the highest form to which time would bring him, the last mutation of all! The road of man's evolution was a circular one, returning to its beginning!
From the earth's bosom had risen the first crude organisms. Then sea-creature and land-creature and mammal and ape to man; and from man it would rise in the future through all the forms we had seen that night. There would be super-men, bodiless heads, pure brains; only to be changed by the last mutation of all into the protoplasm from which first it had sprung!
I do not know now exactly what followed. I know that I rushed upon that quivering, quiescent mass, calling Pollard's name madly and shouting things I am glad I cannot remember. I know that Dutton was shouting too, with insane laughter, and that as he struck with lunatic howls and fury about the laboratory the crash of breaking glass and the hiss of escaping gases was in my ears. And then from those mingling acids bright flames were leaping and spreading sudden fires that alone, I think now, saved my own sanity.