Why is hemichordates called half-chordates?

Explanation

**Step-by-Step Solution:**

1. **Definition of Hemichordates**: Hemichordates are a phylum of marine animals that exhibit characteristics of both non-chordates (like echinoderms) and chordates.

2. **Characteristics of Non-Chordates**: Hemichordates share certain features with echinoderms, which are non-chordates. These features include:
- A proboscis (a tubular structure).
- A collar region.
- A trunk region.
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