A hydra moves via :

Options

A. nematocysts
B. contraction of the nerve net
C. epitheliomuscular fibres in the epidermis
D. epitheliomuscular fibres in the mesoglea

Explanation

To answer the question "A hydra moves via:", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Hydra's Structure**:
- Hydra is a simple aquatic organism belonging to the phylum Cnidaria. It has a cylindrical body and is attached to a substrate by a structure called the basal disc.

2. **Movement Mechanism**:
- Hydra can move from one location to another despite being primarily attached. It does this through two main methods: gliding along its basal disc and somersaulting.

3. **Role of Epithelial Muscular Cells**:
- The epidermis of Hydra contains epithelial muscular cells. These cells are cylindrical and have unstriated muscle fibers. They play a crucial role in the movement of Hydra.

4. **Movement Types**:
- The gliding movement occurs when the hydra extends its body and moves along the substrate. Somersaulting involves the hydra flipping over itself to change position.

5. **Conclusion**:
- Given the information about how Hydra moves, we can conclude that its movement is primarily facilitated by the epithelial muscular fibers present in the epidermis.

### Final Answer:
- A hydra moves via **epithelial muscular fibers in the epidermis**.

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