lsogamous condition with non - motile gametes is found in :

Options

A. Fucus
B. Chlamydomonas
C. Ulothrix
D. Spirogyra

Answer

To solve the question regarding isogamous conditions with non-motile gametes, we will analyze the options given and determine which organism fits the criteria.

### Step-by-Step Solution:

1. **Understanding Isogamy and Non-Motile Gametes**:
- Isogamy refers to a type of sexual reproduction where the gametes are similar in size and shape.
- Non-motile gametes are those that do not have the ability to move independently.

2. **Analyzing the Options**:
- **Fucus**: This organism is known for having oogamous reproduction, where the male gametes (sperms) are motile and the female gametes (eggs) are non-motile. Thus, Fucus does not fit the criteria of isogamous and non-motile gametes.

- **Chlamydomonas**: This organism exhibits three types of reproduction: isogamous, anisogamous, and oogamous. In isogamous conditions, the gametes are similar, but they are motile. Therefore, Chlamydomonas cannot be the answer as it does not have non-motile gametes in isogamous reproduction.

- **Spirogyra**: This organism reproduces sexually through conjugation, where two similar cells (gametes) align side by side and form conjugation tubes. The gametes are similar in size and shape, making them isogamous. Additionally, these gametes do not move independently, thus they are non-motile. Therefore, Spirogyra fits the criteria of isogamous condition with non-motile gametes.

3. **Conclusion**:
- Based on the analysis, the organism that exhibits isogamous conditions with non-motile gametes is **Spirogyra**.

### Final Answer:
**Spirogyra**