Embryologists can presume the future organs of the embryo in

Options

A. Blastula
B. Early gastrula
C. Morula
D. Post gastrula

Explanation

**Step-by-Step Solution:**

1. **Understanding the Stages of Embryonic Development**: The embryonic development progresses through several stages, namely, the zygote, morula, blastula, and gastrula.

2. **Identifying the Key Stages**:
- The **morula** stage is a solid ball of cells formed after several divisions of the zygote.
- The **blastula** stage follows, where the morula transforms into a hollow sphere of cells.
- The **gastrula** stage is characterized by the formation of three germ layers: ectoderm, mesoderm, and endoderm.

3. **Recognizing the Process of Gastrulation**: The transition from the morula to the gastrula is known as gastrulation. It is during this process that the cells begin to differentiate into various types.

4. **Determining When Organ Formation Begins**: Organ formation starts during the gastrula stage. Therefore, while the early gastrula stage does not yet have fully formed organs, it is in the later gastrula and post-gastrula stages that organogenesis occurs.

5. **Evaluating the Given Options**:
- **Blastula**: Incorrect, as organ formation does not occur here.
- **Early Gastrula**: Incorrect, as organ formation begins after this stage.
- **Morula**: Incorrect, as this stage is before gastrulation.
- **Post-Gastrula**: Correct, as this stage is when organ formation is actively taking place.

6. **Conclusion**: The correct answer is that embryologists can presume the future organs of the embryo in the post-gastrula stage.

**Final Answer**: Option 4 - Post-Gastrula

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