To whom his question was addressed no one knows.

"What on earth is that? I don't understand..."

A late lorry rumbled down Herzen Street, making the old walls of the Institute shake. The shallow glass bowl with pipettes tinkled on the table.

The Professor turned pale and put his hands over the microscope, like a mother whose child is threatened by danger. There could now be no question of Persikov turning the knob. Oh no, now he was afraid that some external force might push what he had seen out of his field of vision.

It was a full white morning with a strip of gold which cut across the Institute's cream porch when the Professor left the microscope and walked over to the window on stiff legs. With trembling fingers he pressed a button, dense black shutters blotted out the morning and a wise scholarly night descended on the room. Sallow and inspired, Persikov placed his feet apart, staring at the parquet floor with his watering eyes, and exclaimed: "But how can it be? It's monstrous! Quite monstrous, gentlemen," he repeated, addressing the toads in the terrarium, who were asleep and made no reply.

He paused, then went over to the button, raised the shutters, turned out all the lights and looked into the microscope. His face grew tense and he raised his bushy yellow eyebrows.

"Aha, aha," he muttered. "It's gone. I see. I understand," he drawled, staring with crazed and inspired eyes at the extinguished light overhead.

"It's simple."

Again he let down the hissing shutters and put on the light. Then looked into the microscope and grinned happily, almost greedily.

"I'll catch it," he said solemnly and gravely, crooking his finger.

"I'll catch it. Perhaps the sun will do it too."

The shutters shot up once more. Now you could see the sun. It was shining on the walls of the Institute and slanting down onto the pavements of Herzen Street. The Professor looked through the window, working out where the sun would be in the afternoon. He kept stepping back and forwards, doing a little dance, and eventually lay stomach down on the window-sill.

After that he got down to some important and mysterious work. He covered the microscope with a bell glass. Then he melted a piece of sealing-wax in the bluish flame of the Bun-sen burner, sealed the edge of the glass to the table and made a thumb print on the blobs of wax. Finally he turned off the gas and went out, locking the laboratory door firmly behind him.

There was semi-darkness in the Institute corridors.

The Professor reached Pankrat's door and knocked for a long time to no effect. At last something inside growled like a watchdog, coughed and snorted and Pankrat appeared in the lighted doorway wearing long striped underpants tied at the ankles. His eyes glared wildly at the scientist and he whimpered softly with sleep.

"I must apologise for waking you up, Pankrat," said the Professor, peering at him over his spectacles. "But please don't go into my laboratory this morning, dear chap. I've left some work there that must on no account be moved. Understand?"

"Grrr, yessir," Pankrat replied, not understanding a thing.

He staggered a bit and growled.

"Now listen here, Pankrat, you just wake up," the zoologist ordered, prodding him lightly in the ribs, which produced a look of fright on Pankrat's face and a glimmer of comprehension in his eyes. "I've locked the laboratory," Persikov went on, "so you need not clean it until I come back.

Understand?"

"Yessir," Pankrat croaked.

"That's fine then, go back to bed."

Pankrat turned round, disappeared inside and collapsed onto the bed.

The Professor went into the vestibule. Putting on his grey summer coat and soft hat, he remembered what he had observed in the microscope and stared at his galoshes for a few seconds, as if seeing them for the first time. Then he put on the left galosh and tried to put the right one over it, but it wouldn't go on.

"What an incredible coincidence that he called me away," said the scientist. "Otherwise I would never have noticed it. But what does it mean?

The devil only knows!.."

The Professor smiled, squinted at his galoshes, took off the left one and put on the right. "Good heavens! One can't even imagine all the consequences..." The Professor prodded off the left galosh, which had irritated him by not going on top of the right, and walked to the front door wearing one galosh only. He also lost his handkerchief and went out, slamming the heavy door. On the porch he searched in his pockets for some matches, patting his sides, found them eventually and set off down the street with an unlit cigarette in his mouth.

The scientist did not meet a soul all the way to the church. There he threw back his head and stared at the golden dome.