How do annelid animals differ from arthropods?

Explanation

To differentiate between annelid animals and arthropods, we can follow these steps:

### Step-by-Step Solution:

1. **Body Cavity**:
- **Annelids**: They possess a true coelom, which is a fluid-filled body cavity completely lined by mesoderm.
- **Arthropods**: Their body cavity is known as a hemocoel, which is filled with blood and is not completely lined by mesoderm.

...