select the incorrect statement about the reproductive system of male cockroach.

Options

A. Vasa deferentia - Open into the ejaculatory duct via seminal vesicle.
B. Seminal vesicles - 1 pair
C. Mushroom gland - It opens in phallic gland .
D. Ejaculatory duct - Both seminal vesicles form a single ejaculatory duct.

Answer

To determine the incorrect statement about the reproductive system of the male cockroach, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding the Reproductive System of Male Cockroach**:
- The male cockroach has a well-defined reproductive system that includes structures such as the vas deferens, seminal vesicles, mushroom glands, and ejaculatory duct.

2. **Analyzing Each Option**:
- **Option 1**: "Vas deferens opens into the ejaculatory duct via the seminal vesicle."
- This statement is correct. The vas deferens does indeed open into the ejaculatory duct through the seminal vesicle where sperm is stored.

- **Option 2**: "Seminal vesicle has only one pair."
- This statement is incorrect. The male cockroach has a pair of seminal vesicles, meaning there are two seminal vesicles, not just one pair. Therefore, this option is also incorrect.

- **Option 3**: "Mushroom gland opens into the phallic gland."
- This statement is incorrect. The mushroom glands do not open into the phallic gland. Instead, they serve as accessory reproductive structures and are involved in the production of seminal fluid. Thus, this is the incorrect statement regarding the reproductive system of male cockroach.

- **Option 4**: "Both seminal vesicles form a single ejaculatory duct."
- This statement is correct. The two seminal vesicles do converge to form a single ejaculatory duct.

3. **Conclusion**:
- After analyzing all options, the incorrect statement about the reproductive system of the male cockroach is **Option 3**: "Mushroom gland opens into the phallic gland."

### Final Answer:
The incorrect statement about the reproductive system of the male cockroach is **Option 3**.