Brain in earthworm is formed of

Options

A. subharyngeal ganglia
B. infrapharyngeal ganglia
C. suprapharyngeal ganglia
D. all of the above

Answer

To answer the question "Brain in earthworm is formed of," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Nervous System of Earthworm**:
The nervous system of an earthworm is divided into three main parts: the Central Nervous System (CNS), the Peripheral Nervous System, and the Sympathetic Nervous System.

**Hint**: Remember the three divisions of the nervous system in earthworms.

2. **Identifying the Components of the CNS**:
The CNS consists of a bilobed brain, which is also referred to as cerebral ganglia. This brain is crucial for the earthworm's nervous functions.

**Hint**: Focus on the term "bilobed brain" and its alternative name.

3. **Understanding the Structure of the Brain**:
The brain of the earthworm is made up of two main ganglia: the supra-pharyngeal ganglia and the sub-pharyngeal ganglia.

**Hint**: Recall the two specific ganglia that form the brain.

4. **Recognizing the Connections**:
From the brain, a pair of circumpharyngeal connectives arise, which encircle the pharynx and connect to the sub-pharyngeal ganglia. This forms a nerve ring around the pharynx.

**Hint**: Visualize how the connectives encircle the pharynx and connect the ganglia.

5. **Determining the Correct Answer**:
Given the options:
- Sub-pharyngeal ganglia
- Infra-pharyngeal ganglia
- Supra-pharyngeal ganglia
- All of the above

The correct answer is that the brain in earthworm is primarily formed of the supra-pharyngeal ganglia.

**Hint**: Identify which option correctly represents the components of the brain in earthworms.

### Final Answer:
The brain in an earthworm is formed of the **supra-pharyngeal ganglia**.