Structures present only in `7^(th) and 9^(th)` segmetns of pheretima posthuma are

Answer

To answer the question about the structures present only in the 7th and 9th segments of *Pheretima posthuma*, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Organism**:
- The organism in question is *Pheretima posthuma*, commonly known as the earthworm. It is a fossorial animal that lives in moist soil burrows.

2. **Understand the Body Structure**:
- The body of *Pheretima posthuma* is elongated, cylindrical, and bilaterally symmetrical. It consists of approximately 100 to 120 segments, also known as somites or metamers.

3. **Focus on the Specific Segments**:
- The question specifically asks for structures present in the 7th and 9th segments of the earthworm.

4. **Examine the Blood Vascular System**:
- In the blood vascular system of *Pheretima posthuma*, there are specific structures known as lateral hearts.

5. **Identify the Lateral Hearts**:
- In the 7th and 9th segments, there are pairs of large, thick, muscular, contractile vessels referred to as lateral hearts. These vessels serve as connections between the dorsal and ventral blood vessels.

6. **Conclusion**:
- Therefore, the structures that are present only in the 7th and 9th segments of *Pheretima posthuma* are the **lateral hearts**.

### Final Answer:
The structures present only in the 7th and 9th segments of *Pheretima posthuma* are **lateral hearts**.

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