The two halves of the shell fell into his waiting palms. He stopped his pedalling, brought the halves to his mouth and blew gently so the remaining dust inside was expelled in a little cloud.

‘Ah!’ he exclaimed as I peered over his shoulder. ‘Now you are interested. What do you see?’

I saw a beautiful symmetry: a spiral that curled into delicate miniature and then into infinity, one long, continuous chamber that narrowed and narrowed until it disappeared into itself. ‘What do you see?’ I asked him.

‘I had expected to see chambers, as one does in the chambered nautilus of the Minoans. I do not think they are the same animal.’ He paused, removed his spectacles and pinched at the bridge of his nose. ‘I had planned to measure the chambers to understand how the ratio applies to their interior dimensions.’

He still had a hold of his nose, an odd mannerism. ‘The head of the animal is clearly smaller than the interior space of the shell…a void inside, perhaps a buoyancy control: more air in the chamber and it floats, less and it sinks. But what would be the point of such a frail shell? Surely there’s no protection in that…’

He pressed one of his square-ended fingers against the side of the shell and it flexed under the pressure. I thought it was going to shatter.

Then he pushed the halved shell away, placed a piece of thin timber board on the front edge of the desk, and retrieved the octopus—limp by now, the tentacles draped over his hand and dripping on the floor. The inking of the water had stained the animal a sad grey.

The unblinking eye watched me, maybe pleading, maybe only sad.

He took a scalpel in his left hand, swept his glasses back onto his nose with his right, then took hold of the animal and peered at it again. The returned stare did not disconcert him at all. ‘Every argonaut we have ever studied has been a female. No one’s ever seen a male. Or perhaps we have but none of us has recognised it. Might be an animal we know well, but the connection has never been made.’

‘What are you going to do now?’ I asked. He rolled the scalpel in his fingers.

‘Dissect it,’ he replied. ‘And in the morning, fry it in biscuit crumbs. I do hope you’ll join me.’

I laughed despite myself, then told him it was late and that I must take my leave. He pantomimed dejection, poking his lower lip out comically, and something in me responded to the foolery. I made a little wave across the cabin to him and backed out through the door.

In the tight passageway outside, my father was snoring softly in his bed, his head turned outwards towards me. Argyle’s bunk was empty: another watch through the night.