Balanus differs from Lepas in being

Options

A. Sessile
B. Stalked
C. Absence of cement glands
D. Absence of mantle.

Answer

To solve the question "Balanus differs from Lepas in being," we will analyze the characteristics of both organisms and compare them step by step.

### Step-by-Step Solution:

1. **Identify the Organisms**:
- Balanus and Lepas are both types of barnacles that belong to the class Cirripedia within the phylum Arthropoda.

2. **Understand Their Characteristics**:
- Balanus is known to be a sessile organism, meaning it is fixed in one place and does not move.
- Lepas, on the other hand, is typically stalked, meaning it has a stalk that attaches it to a substrate but allows some mobility.

3. **Evaluate the Options**:
- **Option 1: Sessile** - This suggests that Balanus is immobile, which is true.
- **Option 2: Stalked** - This is incorrect for Balanus, as it is not stalked.
- **Option 3: Absence of Cement Glands** - Both Balanus and Lepas have cement glands, so this option is incorrect.
- **Option 4: Absence of Mantle** - Both organisms have a mantle, making this option incorrect as well.

4. **Conclusion**:
- The only correct distinguishing feature is that Balanus is sessile, while Lepas is not. Therefore, the correct answer is **Option 1: Sessile**.

### Final Answer:
Balanus differs from Lepas in being **sessile**.