Mitotic stages are not observed in

Options

A. Saccaharomyces
B. E. coli
C. Cosmarium
D. Chlorella.

Answer

### Step-by-Step Solution:

1. **Understanding Mitosis**:
- Mitosis is a type of cell division that results in two daughter cells, each having the same number of chromosomes as the parent nucleus. It is a characteristic feature of eukaryotic cells.

2. **Identifying Prokaryotes vs. Eukaryotes**:
- Prokaryotes (like bacteria) do not undergo mitosis. Instead, they reproduce through a process called binary fission. Eukaryotes, on the other hand, undergo mitosis.

3. **Analyzing the Options**:
- **Saccharomyces**: This is a genus of yeast, which is a eukaryote. Therefore, it undergoes mitosis.
- **E. coli**: This is a gram-negative bacterium and a prokaryote. Prokaryotes do not undergo mitosis but reproduce by binary fission. Thus, mitotic stages are not observed in E. coli.
- **Cosmarium**: This is a genus of green algae, which are eukaryotes. Therefore, it undergoes mitosis.
- **Chlorella**: This is also a genus of green algae and is eukaryotic. Hence, it undergoes mitosis.

4. **Conclusion**:
- Among the options provided, the only organism that does not exhibit mitotic stages is **E. coli**, as it is a prokaryote.

### Final Answer:
- **Mitotic stages are not observed in E. coli.**

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