Read the text and complete it with the missing parts.

Do jellyfish sleep?
Worms and fish do it. Birds and bees do it. But do jellyfish fall asleep?

It was after midnight ... where the jellyfish were kept. They left the lights off and walked through the room by the glow of their cellphones. The students did not tell anyone that they were doing this. The secret they were keeping was a “totally crazy” experiment aimed at finding out whether jellyfish sleep.

A few weeks before, ... whether jellyfish needed to sleep. “Of course not,” said one of them. “Sleep helps ... . Jellyfish are so simple they don’t even have brains. How could they possibly share the need to sleep?” The others weren’t so sure, but they wanted to find out.

The three students designed an experiment to test different behaviors and see if the jellyfish were asleep. They watched the animals to see how they moved, and ... when they were resting. It turned out that the jellyfish moved about 30 percent less at night. It was also harder to get their attention.

Months of late-night studying led to amazing results. Young scientists reported ... sleeplike behavior. This made it the first animal without a brain known to do so. The results suggest ... life, as the jellyfish group of animals first arose about 700 million years ago, and has stuck with us ever since.