I was indeed enthralled by their creatures; yet my attention often strayed to themselves, isolated for so much of their time here in this tank, this test tube; as though some superhuman experimenter had singled them out for study, hoping to gain through observation of their mutual reactions new understanding of the human species.

They showed me newts, lizards, frogs; and also (even more distant cousins of Queen Victoria and Jesus Christ) innumerable flies imprisoned in bottles. Some of these creatures were normal products of evolution; some were precious monstrosities, evoked by human ingenuity, and kept alive by a more than maternal devotion. Ordinary newts, with their bladelike tails and inadequate legs (as though copied from a small child's drawing), hung suspended in the water, or glided through the subaqueous jungle, or clambered into the air. But a few were patently and shockingly not ordinary. One such creature miserably supported the burden of two heads. Another carried a half-formed twin attached, to his back. Turning from these oddities, I was shown a normal crested newt (called Archibald). He was induced to display his flame like ornament by the infuriating sight of his own reflection in a bit of mirror. An axolotl, a pallid and feebly animated sausage, inadequately quadruped, stared vacuously, unconscious of his significance for science. Little black lizards, mercurial in the girl's warm hand, were slender as snakes. A unique snake displayed vestigial limbs. Toads lumbered over stones and herbage, bestirring themselves for the chopped meat that was dropped for them. Swarms of little crustaceans, mere fidgeting points of life, explored their bit of ocean or pond for food. Snails clung to leaves or stones. It was pointed out to me that the spiral of the shell was generally coiled clockwise, but occasionally in the opposite direction. And this oddity, I was told, was of special interest because its inheritance depended on the mother alone. The bodies of these creatures, it seems, are asymmetrical through and through, and the dextral and sinistral individuals are mirror images of each other. The young biologist delighted to explain that, since the genital organ is on one side of the head alone, dextrals and sinistrals could never mate with each other, but only with their own kind.

Throughout this scientific exposition, the two humans maintained their banter, snowballing each other with argument, evidence and technical terms. I heard much of allelomorphs, of dominants and recessives, of haploid, of polymorphic varieties, of the exact location of genes on chromosomes.

Leaving the tanks, the young man selected from a certain shelf a certain bottle. There were scores, hundreds, of such bottles, each housing a population of flies; and each population was the issue of some planned interbreeding. A whiff of ether reduced the selected population to temporary impotence, so that they could be poured out on a microscope slide for observation. As I peered through the instrument, the couple spoke of the minute significant differences that I should see, the ruddier and the yellower eyes, the hairy or bald bodies, the stumpy or long antennae, the serviceable or crippled wings. "We have now," the young man said, "recorded nearly a million mutations." His companion took up the thread. "Mostly they are lethal, or at best indifferent; but with them we have mapped out on the chromosomes practically the whole inheritance mechanism of this species." He displayed a printed volume wherein all this work was recorded. "Someday," he said, "our ancestors will have an equally full account of inheritance in man, covering his physical and his mental characters, down to the least idiosyncrasy. The job will, of course, be far more complicated; but there is little doubt that we shall in time analyse out the whole mechanism of human inheritance, and so the basic structure of human nature." The girl continued the theme. "In the end," she said, "we shall breed men as we breed horses and dogs and cattle, creating different types for different functions within the world society; lovers of the tropics and of the arctic, of mining and of flying, of leadership and of obedience, of creative action and of routine, of interplanetary exploration and of terrestrial homekeeping." The young man smiled at me, and winked. He said, "She is rather uncritically sublimating her maternal instinct. Unconsciously, she would like to mother the whole lot." The girl laughed, and replied spiritedly, "Muddleheaded amateur psychologist!"

The show was now over, and the couple were preparing to leave the Department. Taking his mackintosh from behind a door, the young geneticist said, "Well, now you have seen a little of our world, perhaps you can understand why we are confident in science." I concluded my little speech of thanks rather tactlessly, by remarking that science had been said to give power without wisdom.