time by Cunningham himself. It had apparently made no difference where the victims had been — two in full sunlight, one in the darkness of the cave. More proof, if any were needed, that the creatures could see in both grades of illumination. It was not strictly a carrion eater, however; Cunningham remembered that carnivore that had accompanied its victim into the centipede's jaws. It was obviously capable of overcoming the man, but had twice retreated precipitately when it had excellent opportunities to attack him. What was it, then, that drew the creature to scenes of combat and bloodshed, but frightened it away from a man; that frightened, indeed, all of these creatures?
On any planet that had a respectable atmosphere, Cunningham would have taken one answer for granted — scent. In his mind, however, organs of smell were associated with breathing apparatus, which these creatures obviously lacked.
Don't ask why he took so long. You may think that the terrific adaptability evidenced by those strange eyes would be clue enough; or perhaps you may be in a mood to excuse him. Columbus probably excused those of his friends who failed to solve the egg problem.
Of course, he got it at last, and was properly annoyed with himself for taking so long about it. An eye, to us, is an organ for forming images of the source of such radiation as may fall on it; and a nose is a gadget that tells its owner of the presence of molecules. He needs his imagination to picture the source of the latter. But what would you call an organ that forms a picture of the source of smell?
For that was just what those “eyes” did. In the nearly perfect vacuum of this little world's surface, gases diffused at high speed — and their molecules traveled in practically straight lines. There was nothing wrong with the idea of a pinhole camera eye, whose retina was composed of olfactory nerve endings rather than the rods and cones of photosensitive organs.
That seemed to account for everything. Of course the creatures were indifferent to the amount of light reflected from the object they examined. The glare of the open spaces under Deneb's rays, and the relative blackness of a cave, were all one to them — provided something were diffusing molecules in the neighborhood. And what doesn't? Every substance, solid or liquid, has its vapor pressure; under Deneb's rays even some rather unlikely materials probably vaporized enough to affect the organs of these life forms — metals, particularly. The life fluid of the creatures was obviously metal — probably lead, tin, bismuth, or some similar metals, or still more probably, several of them in a mixture that carried the substances vital to the life of their body cells. Probably much of the makeup of those cells was in the form of colloidal metals.
But that was the business of the biochemists. Cunningham amused himself for a time by imagining the analogy between smell and color which must exist here; light gases, such as oxygen and nitrogen, must be rare, and the tiny quantities that leaked from his suit would be absolutely new to the creatures that intercepted them. He must have affected their nervous systems the way fire did those of terrestrial wild animals. No wonder even the centipede had thought discretion the better part of valor!
With his less essential problem solved for the nonce. Cunningham turned his attention to that of his own survival; and he had not pondered many moments when he realized that this, as well, might be solved. He began slowly to smile, as the discrete fragments of an idea began to sort themselves out and fit properly together in his mind — an idea that involved the vapor pressure of metallic blood, the leaking qualities of the utility suits worn by his erstwhile assistants, and the bloodthirstiness of his many-legged acquaintances of the day; and he had few doubts about any of those qualities. The plan became complete, to his satisfaction; and with a smile on his face, he settled himself to watch until sunset.
Deneb had already crossed a considerable arc of the sky. Cunningham did not know just how long he had, as he lacked a watch, and it was soon borne in on him that time passes much more slowly when there is nothing to occupy it. As the afternoon drew on, he was forced away from the cave mouth; for the descending star was beginning to shine in. Just before sunset, he was crowded against one side; for Deneb's fierce rays shone straight through the entrance and onto the opposite wall, leaving very little space not directly illuminated. Cunningham drew a sigh of relief for more reasons than one when the upper limb of the deadly luminary finally disappeared.
His specimens had long since recovered from their fright, and left the cavern; he had not tried to stop them. Now, however, he emerged from the low entryway and went directly to the nearest dust dune, which was barely visible in the starlight. A few moments' search was rewarded with one of the squirming plant-eaters, which he carried back into the shelter; then, illuminating the scene carefully with the small torch that was clipped to the waist of his suit, he made a fair-sized pile of dust, gouged a long groove in the top with his toe; with the aid of the same stone he had used before, he killed the plant-eater and poured its “blood” into the dust mold.
The fluid was metallic, all right; it cooled quickly, and in two or three minutes Cunningham had a silvery rod about as thick as a pencil and five or six inches long. He had been a little worried about the centipede at first; but the creature was either not in line to “see” into the cave, or had dug in for the night like its victims.
Cunningham took the rod, which was about as pliable as a strip of solder of the same dimensions, and, extinguishing the torch, made his way in a series of short, careful leaps to the stranded spaceship. There was no sign of the men, and they had taken their welding equipment inside with them — that is, if they had ever had it out; Cunningham had not been able to watch them for the last hour of daylight. The hull was still jacked up, however; and the naturalist eased himself under it and began to examine the damage once more using the torch. It was about as he had deduced from the conversation of the men; and with a smile, he took the little metal stick and went to work. He was busy for some time under the hull, and once he emerged, found another plant-eater, and went back underneath. After he had finished, he walked once around the ship, checking each of the air locks and finding them sealed, as he had expected.
He showed neither surprise nor disappointment at this; and without further ceremony he made his way back to the cave, which he had a little trouble finding in the starlight. He made a large pile of the dust for insulation rather than bedding, lay down on it, and tried to sleep. He had very little success, as he might have expected.
Night, in consequence, seemed unbearably long; and he almost regretted his star study of the previous darkness, for now he was able to see that sunrise was still distant, rather than bolster his morale with the hope that Deneb would be in the sky the next time he opened his eyes. The time finally came, however, when the hilltops across the valley leaped one by one into brilliance as the sunlight caught them; and Cunningham rose and stretched himself. He was stiff and cramped, for a spacesuit makes a poor sleeping costume even on a better bed than a stone floor.
As the light reached the spaceship and turned it into a blazing silvery spindle, the air lock opened. Cunningham had been sure that the men were in a hurry to finish their task, and were probably awaiting the sun almost as eagerly as he in order to work efficiently; he had planned on this basis.
Malmeson was the first to leap to the ground, judging by their conversation, which came clearly through Cunningham's phones. He turned back, and his companion handed down to him the bulky diode welder and a stack of filler rods. Then both men made their way forward to the dent where they were to work. Apparently they failed to notice the bits of loose metal lying on the scene — perhaps they had done some filing themselves the day before. At any rate, there was no mention of it as Malmeson lay down and slid under the hull, and the other began handing equipment in to him.
Plant-eaters were beginning to struggle out of their dust beds as the connections were completed, and the torch started to flame. Cunningham nodded in pleasure as he noted this; things could scarcely have been timed better had the men been consciously co-operating. He actually emerged from the cave, keeping in the shadow of the hillock, to increase his field of view; but for several minutes nothing but plant-eaters could be seen moving.
He was beginning to fear that his invited guests were too distant to receive their call, when his eye caught a glimpse of a long, black body slipping silently over the dunes toward the ship. He smiled in satisfaction; and then his eyebrows suddenly rose as he saw a second snaky form following the tracks of the first.
He looked quickly across his full field of view, and was rewarded by the sight of four more of the monsters — all heading at breakneck speed straight for the spaceship. The beacon he had lighted had reached more eyes than he had expected. He was sure that the men were armed, and had never intended that they actually be overcome by the creatures; he had counted on a temporary distraction that would let him reach the air lock unopposed.
He stood up, and braced himself for the dash, as Malmeson's helper saw the first of the charging centipedes and called the welder from his work. Malmeson barely had time to gain his feet when the first pair of attackers
