Which of the following statements is not correct w.r.t. earthworm ?

Options

A. One pair of testis in segment 9
B. One pair of ovary in segment 13
C. Protandrous condition
D. Cross-fertilization

Answer

To determine which statement is not correct with respect to earthworms, we can analyze each option provided:

1. **One pair of testes in segment 9**: This statement is incorrect. Earthworms actually have two pairs of testes located in segments 10 and 11. Therefore, this statement does not accurately describe the anatomy of earthworms.

2. **One pair of ovaries in segment 13**: This statement is correct. Earthworms possess one pair of ovaries that are located at the intersegmental septum between segments 12 and 13. Thus, this statement accurately reflects the reproductive anatomy of earthworms.

3. **Protandrous condition**: This statement is correct. Earthworms exhibit protandry, meaning that the male reproductive organs mature before the female reproductive organs. This characteristic helps facilitate cross-fertilization.

4. **Cross-fertilization**: This statement is also correct. Although earthworms are hermaphroditic (having both male and female reproductive organs), they typically engage in cross-fertilization rather than self-fertilization due to the protandrous condition.

Based on this analysis, the statement that is not correct with respect to earthworms is: **"One pair of testes in segment 9."**

### Step-by-Step Solution:
1. **Identify the statements regarding earthworm anatomy and reproduction.**
- Statements to analyze: One pair of testes in segment 9, one pair of ovaries in segment 13, protandrous condition, and cross-fertilization.

2. **Evaluate the first statement about testes.**
- Check the anatomical details: Earthworms have two pairs of testes in segments 10 and 11, not one pair in segment 9.

3. **Evaluate the second statement about ovaries.**
- Confirm the location: Earthworms have one pair of ovaries located at the intersegmental septum between segments 12 and 13.

4. **Evaluate the third statement about protandry.**
- Understand the concept: Earthworms mature male organs before female organs, confirming the protandrous condition.

5. **Evaluate the fourth statement about cross-fertilization.**
- Recognize the reproductive behavior: Earthworms usually engage in cross-fertilization due to their hermaphroditic nature and protandrous condition.

6. **Conclude which statement is incorrect.**
- The statement "One pair of testes in segment 9" is incorrect, as earthworms have two pairs of testes in segments 10 and 11.