The eggs in Eutherian mammals are :

Options

A. Megalecithal
B. Telolecithal
C. Microlecithal
D. Alecithal

Answer

**Step-by-Step Solution:**

1. **Understanding Eutherian Mammals**: Eutherian mammals, also known as placental mammals, are characterized by their reproductive system, where the embryo develops inside the uterus and is nourished through a placenta.

2. **Types of Eggs**: There are different classifications of eggs based on the amount of yolk they contain and the pattern of cleavage during development. The main types mentioned are:
- **Megalacetal Eggs**: These eggs have a large amount of yolk, and the cleavage occurs only on one side, leading to uneven cell division. This type is typically found in birds.
- **Telolacetal Eggs**: Similar to megalacetal eggs, these also have a large yolk and one-sided cleavage, found in birds as well.
- **Microlacetal Eggs**: These eggs contain a small amount of yolk, allowing for holoblastic cleavage, which means the egg divides completely into smaller cells. This type is characteristic of eutherian mammals.
- **Unlethal Eggs**: These eggs have negligible yolk and are found in organisms like Amphioxus.

3. **Identifying the Correct Type for Eutherian Mammals**: Since eutherian mammals exhibit microlacetal eggs, which are characterized by a small amount of yolk and complete cleavage, we conclude that the correct answer is microlacetal.

4. **Conclusion**: The eggs in eutherian mammals are classified as microlacetal eggs.

**Final Answer**: The eggs in Eutherian mammals are microlacetal.

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