Eggs of placental mammals are

Options

A. Homolecithal
B. Alecithal
C. Microlecithal
D. Mesolecithal

Answer

**Step-by-Step Solution:**

1. **Understanding Egg Types**: Begin by familiarizing yourself with the different types of eggs based on yolk content. The main types are homolacetal, alacetal, microlecetal, and mesolecetal.

2. **Homolacetal Eggs**: These eggs, also known as isolacetal eggs, contain a small amount of yolk that is uniformly distributed throughout the ooplasm. Since placental mammals do not have this type of egg, we can eliminate this option.

3. **Alacetal Eggs**: Alacetal eggs are characterized by having negligible or no yolk. In placental mammals, the embryo receives nutrition directly from the placenta rather than from yolk, making this type of egg applicable. Therefore, this option is correct.

4. **Microlecetal Eggs**: Microlecetal eggs contain a small amount of yolk. However, since placental mammals do not rely on yolk for nutrition, this option is incorrect.

5. **Mesolecetal Eggs**: Mesolecetal eggs have yolk concentrated at one end (the vegetal pole), while the other end (the animal pole) contains the nucleus and cytoplasm. Since placental mammals do not have this type of egg, this option can also be eliminated.

6. **Conclusion**: After analyzing all the options, we conclude that the eggs of placental mammals are alacetal, characterized by negligible or no yolk.

**Final Answer**: The eggs of placental mammals are alacetal (negligible or no yolk).

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