1. How does it move? It is a worm: long, bending, thrashing or gliding

What kind of worm?

Look at the surface: segments, bristles, cilia, or a smooth shiny skin.

1. Smooth and shiny, tapered at both ends, thrashing in S-curves→ Nematodes
2. Segmented, with bundles of bristles along the sides→ Aquatic worms
3. Soft and flat, gliding smoothly, no segments or bristles→ Small flatworms
4. Telescopes in and out, creeps like a leech, crowns at the front→ Rotifers
5. A single long cell that suddenly contracts to a fraction of its length→ Spirostomum

Not sure? How to judge size by the field of view · This step looks wrong