II

Davis followed that compact discourse in a mood of unusual self–forgetfulness. It was, he found, as refreshing as good drink, and as little likely to linger in the system. And even the new member betrayed a certain humility in his attention.

But he still felt it was his duty to himself to talk.

'Those cosmic rays of yours,' he said. 'They are the most difficult part of your story. They aren't radiations. They aren't protons. What are they? They go sleeting through the universe incessantly, day and night, going from nowhere to nowhere. For the life of me I find that hard to imagine.'

'They must come from somewhere,' said a quiet little man with an air of producing a very special contribution to the discussion.

'We note their existence,' said the old gentleman. 'We watch them but we draw no premature conclusions. They are infinitesimal particles flying at an inconceivable velocity. They come from all directions of outer space. And that's as much as we know about them. If I put out my finger like that for a second or so, there's only just a dozen or so gone through it in a second. And no harm done. Which is just as well. There's more up above us in the outer atmosphere. But fortunately they get reflected and absorbed. You know we have a sort of filtering halo about the earth, a sort of cloak of electrons, which keeps off any excess of these radiations.'

'That Heaviside layer,' a stout rufous man, who had apparently been asleep, interpolated.

'And what may that be?' asked the barrister.

'It's a beautiful sample of scientific terminology,' said the stout rufous man still somnolently. 'This Heaviside layer, so far as I can understand it, is called so, because firstly it isn't heavy, secondly it hasn't any side, and thirdly it is almost as much a layer as—as a rheumatic chill or a glow of indignation. Go on, Professor.'

His eyes, which had been partly open, closed again.

'You said,' said the examining barrister, 'that fortunately they are kept off. Why—fortunately? May I ask?'

'My thankfulness may have been a little unwarranted,' said the old gentleman. 'But these cosmic rays have a lot of energy, considering their size. They knock atoms about when they hit them. And we and our belongings are made of atoms. A lot of them, a great lot of them, a real douche of cosmic rays, might cause all sorts of tissue diseases, blow up mines, strike the matches in our pockets. But as it is they don't often hit even one atom—quantitatively they're more ineffective even than that infinitesimal quantity of radiation that is always coming up from the radium in the earth; and so Nature is able to clean up any little speck of mess that occurs.'

'Not always,' said Foxfield suddenly.

'I've heard of that idea you're alluding to, Mr. Foxfield,' said the old gentleman. 'You mean that idea about the chromosomes.'

'Now tell me,' said the barrister, relapsing for a moment. 'I've heard somewhere before of this idea you're speaking of. I'm told these cosmic rays affect—what is it you call them?—mutations.'

'I have no doubt of it,' said Foxfield.

'You'll find no physicist to encourage you,' said the old gentleman.

'Or contradict me,' said Foxfield.

'Aye, aye,' said the old gentleman cheerfully. 'It's a case of not proven.'

'But what is this?' asked Davis. 'Do you mean that these—these cosmic rays may affect heredity—inheritance?'

'I should be inclined to say they must,' said Foxfield.

'But why them in particular?' asked the barrister.

'Because we have eliminated almost every other possible cause for changes in the chromosomes.'

'It's a most extraordinary thing,' said the rufous man, slowly waking up and passing by swift stages from sleepiness to a bright alertness.

'The chromosomes,' said Foxfield, 'the germinal elements, have very complicated and enormous molecules. They are rather elaborately protected from most types of disturbance. They have a sort of independence of the parent body. They go their way alone.'

'Transmission of acquired characteristics strictly forbidden,' someone interjected.

'It seems to be. But the X rays, the Gamma rays, and particularly these cosmic rays can get through, and so, I reason, they must get through—to start something fresh. Since something fresh is always being started.'

And now it was Foxfield's turn to answer intelligent questions and give a brief lecture.

He summarized the new realizations of the past twenty–five years about mutations and survival almost as expertly as the old professor had elucidated his atoms. He showed how the changing of species bit by bit, by imperceptible gradations, which the early Darwinians had stressed, had given place in modern evolutionary theory to a realization of the frequency of extensive simultaneous sports and mutations. And there was nothing in the circumstances of an animal species which could explain these sports and mutations. And so it was that Foxfield was compelled to think they were produced by some penetrating exterior force.

'But why not Providence?' asked the quiet man.

'Because the vast majority of these mutations are aimless and useless,' said Foxfield.

'And so, having eliminated everything else,' said the barrister, 'you lay the burden of change and mutation—and in fact all the responsibility for evolution—on those little cosmic rays! Countless myriads fly by and miss. Then one hits—Ping! Ping!—and we get a double–headed calf or a superman.'

'What an unsettled universe it is!' said someone.