Which is not correct for sponges?

Options

A. Internal fertilization
B. external fertilization
C. Gemmule formation
D. Gametes are formed from epidermal cells

Answer

To determine which statement is not correct for sponges, we can analyze the options provided step by step.

### Step-by-Step Solution:

1. **Understanding Sponges' Reproductive System**:
- Sponges are known to be hermaphrodites, meaning they possess both male and female reproductive organs. This allows them to produce both sperm and eggs.

2. **Evaluating Internal Fertilization**:
- The first option states that sponges undergo internal fertilization. This is accurate because, in sponges, sperm is released into the water and can enter another sponge's body to fertilize the eggs internally. Therefore, this option is correct.

3. **Considering External Fertilization**:
- The next option suggests that sponges can undergo external fertilization. However, since sponges are hermaphrodites and typically fertilize internally, this statement is not correct. Thus, this option is a candidate for the answer.

4. **Examining Gemmule Formation**:
- The option regarding gemmule formation states that sponges can form gemmules, which are asexual reproductive structures. This is true, especially in freshwater sponges, which can produce gemmules during unfavorable conditions. Therefore, this option is correct.

5. **Analyzing Gamete Formation**:
- The final option mentions that gametes are formed from epidermal cells. This is incorrect because sponges produce gametes from specialized cells called archaeocytes, not from epidermal cells. Therefore, this statement is also not correct.

6. **Conclusion**:
- After evaluating all the options, we find that both the external fertilization and the statement about gametes being formed from epidermal cells are incorrect. However, since the question asks for which is not correct, we can conclude that the most direct answer is that sponges do not undergo external fertilization.

### Final Answer:
The statement that is not correct for sponges is that they undergo external fertilization.

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