Give two groups of animals showing spiral cleavage.

Explanation

**Step-by-Step Solution:**

1. **Understanding Spiral Cleavage**:
- Spiral cleavage is a type of embryonic development where the cells divide in a spiral arrangement. This occurs after the fertilization of the egg, leading to a unique pattern of cell division.

2. **Characteristics of Spiral Cleavage**:
- In spiral cleavage, the upper cells (or blastomeres) divide in a different plane than the lower cells. This results in a spiral pattern of cell arrangement, which can be observed under a microscope.

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