Which of the following not a hermaphrodite animal ?

Options

A. Hirudinaria
B. Earthworm
C. Planaria
D. Nereis

Answer

To determine which of the following animals is not a hermaphrodite, we need to understand the definitions of hermaphroditism and unisexuality.

### Step-by-Step Solution:

1. **Define Hermaphroditism**: Hermaphroditic animals, also known as bisexual animals, possess both male and female reproductive organs within the same individual. This allows them to produce both sperm and eggs.

2. **Identify Unisexual Animals**: Unisexual animals, on the other hand, have distinct male and female individuals. They can only produce one type of gamete (either sperm or eggs).

3. **Analyze the Given Options**:
- **Hirudinaria**: This is a blood-sucking leech, which is a hermaphrodite as it has both male and female reproductive organs.
- **Earthworm (Ferritima postuma)**: Like Hirudinaria, earthworms are also hermaphrodites.
- **Planaria**: These flatworms are also hermaphroditic, possessing both male and female reproductive systems.
- **Nereis**: This is a genus of marine annelids that are known to be dioecious, meaning they have separate male and female individuals. Therefore, Nereis is not a hermaphrodite.

4. **Conclusion**: Based on the analysis, the animal that is not a hermaphrodite is **Nereis**.

### Final Answer:
Nereis is the animal that is not a hermaphrodite.

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