Why ctenophores are commonly called comb-jellies?

Explanation

**Step-by-Step Solution:**

1. **Introduction to Ctenophores**: Ctenophores are a group of marine animals that belong to the phylum Ctenophora. They are primarily found in deep sea environments.

2. **Gelatinous Nature**: These organisms are characterized by their gelatinous body structure. This gives them a jelly-like appearance, which is one of the reasons they are referred to as "jellies."

3. **Presence of Cilia**: Ctenophores possess unique structures known as cilia. These cilia are not just individual hair-like structures; they are fused together to form plates.

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