Meroblastic cleavage is

Options

A. Total
B. Spiral
C. Incomplete
D. Horizontal.

Answer

### Step-by-Step Solution:

1. **Definition of Meroblastic Cleavage**:
- Meroblastic cleavage refers to a type of embryonic development where the cleavage of the egg is partial due to the presence of a large amount of yolk. This means that not the entire egg is divided during the cleavage process.

2. **Characteristics of Meroblastic Cleavage**:
- In meroblastic cleavage, the cleavage furrows do not penetrate through the entire yolk. Instead, they only divide a portion of the egg, leading to incomplete cleavage.

3. **Types of Meroblastic Cleavage**:
- There are two main types of meroblastic cleavage:
- **Discoidal Cleavage**: This occurs in species such as reptiles and birds, where the yolk is concentrated at one end of the egg (telolecithal eggs). The cleavage occurs in a disc-shaped area on top of the yolk.
- **Superficial Cleavage**: This type occurs in some arthropods, where the cleavage furrows form only on the surface of the egg, resulting in a multinucleated condition without complete division of the yolk.

4. **Examples of Organisms**:
- Meroblastic cleavage is commonly observed in reptiles and birds due to their large yolk content. In contrast, organisms with little or no yolk typically undergo holoblastic cleavage, where the entire egg is divided.

5. **Conclusion**:
- Therefore, meroblastic cleavage is characterized by partial and incomplete cleavage due to high yolk content, and it can be classified into discoidal and superficial types.