Which extra-embryonic membrane is excretory in function and is analogous to the kidneys?

Explanation

**Step-by-Step Solution:**

1. **Understanding Extra-embryonic Membranes**: There are four extra-embryonic membranes in mammals: Chorion, Amnion, Allantois, and Yolk sac. Each has distinct functions related to the embryo's development.

2. **Identifying the Functions**:
- **Chorion**: The outermost membrane, primarily protective.
- **Amnion**: Contains amniotic fluid, providing cushioning and protection to the embryo.
- **Yolk sac**: Provides nutrition to the embryo.
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