He could hear sandtrout dropping into the qanat, the swirl of predators eating them.

Water softened the sandtrout, made it pliable. Children learned this early. A bit of saliva teased out the sweet syrup. Leto listened to the splashing. This was a migration of sandtrout come up to the open water, but they could not contain a flowing qanat patrolled by predator fish.

Still they came; still they splashed.

Leto groped on the sand with his right hand until his fingers encountered the leathery skin of a sandtrout. It was the large one he had expected. The creature didn't try to evade him, but moved eagerly onto his flesh. He explored its outline with his free hand -- roughly diamond-shaped. It had no head, no extremities, no eyes, yet it could find water unerringly. With its fellows it could join body to body, locking one on another by the coarse interlacings of extruded cilia until the whole became one large sack-organism enclosing the water, walling off the "poison" from the giant which the sandtrout would become: Shai-Hulud.

The sandtrout squirmed on his hand, elongating, stretching. As it moved, he felt a counterpart elongating and stretching of the vision he had chosen. This thread, not that one. He felt the sandtrout becoming thin, covering more and more of his hand. No sandtrout had ever before encountered a hand such as this one, every cell supersaturated with spice. No other human had ever before lived and reasoned in such a condition. Delicately Leto adjusted his enzyme balance, drawing on the illuminated sureness he'd gained in spice trance. The knowledge from those uncounted lifetimes which blended themselves within him provided the certainty through which he chose the precise adjustments, slaving off the death from an overdose which would engulf him if he relaxed his watchfulness for only a heartbeat. And at the same time he blended himself with the sandtrout, feeding on it, feeding it, learning it. His trance vision provided the template and he followed it precisely.