In chordates primary egg membranes are formed when :–

Options

A. The egg remain with in ovary
B. The egg discharged from ovary
C. The egg passes through oviduct
D. The egg passes out of oviduct

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks when the primary egg membranes are formed in chordates. The primary egg membrane is known as the zona pellucida.

2. **Defining the Zona Pellucida**: The zona pellucida is a glycoprotein layer that surrounds the egg (ova). It is crucial for fertilization as it protects the egg and plays a role in sperm binding.

3. **Formation of Zona Pellucida**: The zona pellucida is formed by the secretion of glycoproteins from the egg itself and the surrounding follicular cells (granulosa cells) during the development of the egg.

4. **Timing of Formation**: The formation of the zona pellucida begins when the egg is still within the ovary. This occurs during the early stages of oocyte development.

5. **Evaluating the Options**:
- **Option A**: Egg remains within the ovary - This is correct as the zona pellucida starts forming while the egg is still in the ovary.
- **Option B**: Egg discharged from ovary - Incorrect, as the zona pellucida has already formed by this time.
- **Option C**: Egg passes through oviduct - Incorrect, as the zona pellucida is already formed before this stage.
- **Option D**: Egg passes out of the body - Incorrect for the same reason as above.

6. **Conclusion**: The correct answer is that the primary egg membranes (zona pellucida) are formed when the egg remains within the ovary.

**Final Answer**: The primary egg membranes in chordates are formed when the egg remains within the ovary.

---