Primitive nervous system is formed in

Options

A. sponge
B. cnidaria
C. echinodermata
D. annelida

Answer

To answer the question "Primitive nervous system is formed in," we will analyze the options provided: Spongy, Cnidaria, Echinodermata, and Annelida.

### Step-by-Step Solution:

**Step 1: Understanding the Nervous System in Sponges**
- Sponges belong to the phylum Porifera.
- They do not have a nervous system; instead, they have a simple organization without nerve cells.

**Step 2: Examining the Nervous System in Cnidaria**
- Cnidarians, which include jellyfish, corals, and sea anemones, have a primitive nervous system.
- Their nervous system is formed by a network of nerve fibers that are scattered throughout the body, often referred to as a nerve net.

**Step 3: Analyzing the Nervous System in Echinodermata**
- Echinoderms, such as starfish and sea urchins, do possess a nervous system.
- However, it is more complex than that of Cnidarians and is not considered primitive.

**Step 4: Investigating the Nervous System in Annelida**
- Annelids, which include earthworms and leeches, have a more advanced nervous system.
- Their nervous system consists of a series of ganglia, with each segment of their body containing a ganglion.

**Conclusion:**
- Based on the analysis, the primitive nervous system is found in Cnidaria, making it the correct answer.

### Final Answer:
The primitive nervous system is formed in **Cnidaria**.

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