Haemocoel occurs in

Options

A. Hydra
B. Snake
C. Earthworm
D. Pila.

Answer

To determine where haemocoel occurs, we need to analyze the options provided: Hydra, Snake, Earthworm, and Pila.

### Step-by-Step Solution:

1. **Understanding Haemocoel**:
- Haemocoel is a type of body cavity found in certain invertebrates, particularly in the phylum Mollusca. It is filled with blood or hemolymph and is part of an open circulatory system.

2. **Analyzing Each Option**:
- **Hydra**:
- Hydra is a freshwater organism belonging to the phylum Cnidaria. It does not have a true coelom (body cavity) but instead has a gastrovascular cavity. Therefore, haemocoel is absent in Hydra.
- **Snake**:
- Snakes are reptiles belonging to the phylum Chordata. They possess a true coelom, but they do not have a haemocoel as they have a closed circulatory system. Thus, haemocoel is absent in snakes.
- **Earthworm**:
- Earthworms belong to the phylum Annelida. They have a true coelom (coelomate) and a closed circulatory system. Therefore, they do not possess a haemocoel.
- **Pila**:
- Pila is a genus of freshwater snails in the phylum Mollusca. Mollusks typically have a haemocoel as part of their open circulatory system. Hence, Pila does contain a haemocoel.

3. **Conclusion**:
- Based on the analysis, the only organism from the options provided that has a haemocoel is **Pila**.

### Final Answer:
Haemocoel occurs in **Pila** (option 4).

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