both are necessarily the same through identical heredity. Evaluation of alien motivations, conversely—"

"Oh, hell," Farrell cut in wearily. "Let's get back to the ship, shall we? We'll all feel more like—"

His right foot gave way beneath him without warning, crushing through the soft ground and throwing him heavily. He sat up at once, and swore in incredulous anger when he found the ankle swelling rapidly inside his boot.

"Sprained! Damn it all!"

Gibson and Stryker, on their knees beside the broken crust of soil, ignored him. Gibson took up a broken length of stick and prodded intently in the cavity, prying out after a moment a glistening two-foot ellipsoid that struggled feebly on the ground.

"A chrysalid," Stryker said, bending to gauge the damage Farrell's heavy boot had done. "In a very close pre-eclosion stage. Look, the protective sheathing has begun to split already."

The thing lay twitching aimlessly, prisoned legs pushing against its shining transparent integument in an instinctive attempt at premature freedom. The movement was purely reflexive; its head, huge-eyed and as large as a man's clenched fist, had been thoroughly crushed under Farrell's heel.

Oddly, its injury touched Farrell even through the pain of his injured foot.

"It's the first passably handsome thing we've seen in this pesthole," he said, "and I've maimed it. Finish it off, will you?"

Stryker grunted, feeling the texture of the imprisoning sheath with curious fingers. "What would it have been in imago, Gib? A giant butterfly?"

"A moth," Gibson said tersely. "Lepidoptera, anyway."

He stood up and ended the chrysalid's strugglings with a bolt from his heat-gun before extending a hand to help Farrell up. "I'd like to examine it closer, but there'll be others. Let's get Arthur out of here."

They went back to the ship by slow stages, pausing now and then while Gibson gathered a small packet of bone fragments from the mudflats and underbrush.

"Some of these are older than others," he explained when Stryker remarked on his selection. "But none are recent. It should help to know their exact age."

An hour later, they were bathed and 

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