The layer absent in the embryos of diploblastic animals is

Options

A. Ectoderm
B. Mesoderm
C. Endoderm
D. Mesoglea

Explanation

To answer the question about the layer absent in the embryos of diploblastic animals, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Classification of Animals**: Animals are classified based on the number of germ layers they possess during embryonic development. The two main categories are diploblastic and triploblastic animals.

2. **Identify Germ Layers**:
- **Diploblastic Animals**: These animals have two germ layers:
- **Ectoderm**: The outermost layer.
- **Endoderm**: The innermost layer.
- **Triploblastic Animals**: These animals have three germ layers:
- **Ectoderm**: The outermost layer.
- **Mesoderm**: The middle layer.
- **Endoderm**: The innermost layer.

3. **Recognize the Absence of a Layer in Diploblastic Animals**: In diploblastic animals, the mesoderm is absent. This is a key distinction between diploblastic and triploblastic organisms.

4. **Clarify the Role of Mesoglia**: While diploblastic animals do have a non-cellular layer called mesoglia between the ectoderm and endoderm, it is not considered a germ layer. Therefore, it does not count as one of the primary germ layers.

5. **Conclusion**: Based on the above understanding, the layer that is absent in the embryos of diploblastic animals is the **mesoderm**.

### Final Answer:
The layer absent in the embryos of diploblastic animals is the **mesoderm**.

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