Wheel Animalcules are

Options

A. Coelenterates
B. Echinoderms
C. Rotifers
D. Protozoans.

Answer

**Step-by-Step Solution:**

1. **Understanding the Term "Animalcules":**
- The term "animalcules" is an older term used to refer to microscopic organisms. It generally describes tiny, often unicellular organisms that are not visible to the naked eye.

2. **Identifying Wheel Animalcules:**
- The specific term "wheel animalcules" refers to a particular group of microscopic organisms known as rotifers. This name comes from the characteristic wheel-like appearance created by the ciliated structures around their mouths.

3. **Classifying Rotifers:**
- Rotifers belong to the phylum Rotifera. They are pseudocoelomate animals, which means they have a body cavity that is not completely lined by mesoderm.

4. **Structure and Function:**
- Rotifers are equipped with a structure called the corona, which consists of several ciliated tufts. These cilia help in locomotion, allowing rotifers to swim in aquatic environments, particularly in freshwater habitats.

5. **Evaluating the Options:**
- The options provided are:
- A) Cilindrates (incorrect, as these are cnidarians)
- B) Echinoderms (incorrect, as these are marine organisms)
- C) Rotifers (correct, as they are the wheel animalcules)
- D) Protozoa (incorrect, as these are unicellular eukaryotes without the corona structure)

6. **Conclusion:**
- Based on the above analysis, the correct answer to the question "Wheel Animalcules are" is **C) Rotifers**.

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